The Senedd Cymru (Members and Elections) Act 2024 (“the Act”) introduced major structural and electoral changes to Senedd Cymru (Welsh Parliament) which took effect for the election on 7 May 2026. These included an increase to the size of the Senedd from 60 to 96 members, and the introduction of a new, Closed Proportional List electoral system. Both provisions marked the culmination of a long-running debate on the size of the Senedd and its electoral system: these were informed by an understanding that the original Senedd was too small, its scrutiny capacity too thinly spread, and the desire to introduce a more proportional electoral system. For two decades, beginning with the Richard Commission (2004), a total of five inquiries produced recommendations on these two elements of Senedd reform. While the Act follows the recommendations to increase the size of the Senedd to between 80 and 100 members, the choice of electoral system differs from the long-term consensus, with most of the recommendations having favoured the Single Transferable Vote. As this blogpost will explore, the potential for further reform of the Senedd’s election system remains a live issue in Welsh politics, and a manifesto commitment of the new Plaid Cymru government.
Due to the significance of Senedd reform and its effect on Welsh democracy, the Act creates a post-implementation review mechanism focussing on specific areas of the Act’s operation and effect. The Act’s explanatory memorandum (para. 200) sets out the Welsh Government’s decision that post-implementation review of the Act should be undertaken by the Senedd. As a result, the Act provides two mechanisms for post-implementation review of its operation and effect, via Senedd committees, together with wider amendments to the boundary review mechanism for Senedd constituencies. This post analyses the mechanisms for post-implementation of the Act’s operation and effect, and considers how any review findings may affect future decisions on Senedd reform.
What are the provisions for post-implementation review?
The Act mandates the use of three, separate mechanisms for post-implementation review of Senedd practices and procedures. First, section 7 requires a motion be tabled before the Senedd to establish a committee to review the possibility of job-sharing of ‘relevant offices’ relating to the Senedd. The relevant offices include Members of the Senedd, the Llywydd (Presiding Officer) and Senedd Commission, and all positions in Welsh Government, including the First Minister. Second, section 19 requires a motion be tabled before the Senedd to establish a committee to review the operation of Parts 1 and 2 of the Act (dealing with the main Senedd reforms), as well as ‘the extent to which the elements of a healthy democracy are present in Wales’. Third, through amendments made to the Democracy and Boundary Commission Cymru Act 2013 (“the 2013 Act”), the Act also creates a boundary review mechanism for the Senedd’s new multi-member constituencies.
Under sections 7 and 19, responsibility falls to the Llywydd to table the review motions (the Llywydd has been involved with previous Senedd reforms, including sponsoring the earlier Senedd and Elections (Wales) Act 2020). Both review motions must take place ‘as soon as practicable’ after the first meeting of the Senedd following the 7 May 2026 election, and not more than six months after the first meeting. As the Senedd met for the first time on 12 May, this creates a deadline of 12 November 2026 for both motions to be tabled before the Senedd. It will be for the Senedd, in the terms of the motion it agrees (if passed at all), to determine those areas that will be reviewed, and how the reviews shall be conducted.
If the Senedd approves a review under either section, the Act requires the relevant committee to lay a report of its findings before the Senedd. This is followed by a requirement on Welsh Ministers to lay a statement setting out their response to the reports. While there are no time limits on this report stage under section 7, the provisions under section 19 require the review to be completed no later than twelve months after the first meeting of the Senedd after the 7 May election. This creates a deadline of 12 May 2027 for the relevant committee to conclude its work and lay the section 19 report before the Senedd.
Finally, though not directly administered by the Act, the amendments made to the 2013 Act create a new boundary review mechanism for Senedd constituencies. These provisions take effect through Schedule 3 of the Act which inserts a new Part 3A into the 2013 Act. Under section 49A of Part 3A, the Democracy and Boundary Commission Cymru (DMCC) must conduct a Senedd constituency boundary review once every review period. The relevant review periods are set out under subsection 5: (a) the period beginning with 1 April 2025 and ending with 30 November 2028; (b) a period of eight years beginning with 1 December 2028; (c) each subsequent period of 8 years.
The Senedd boundary review mechanism holds the possibility of creating a new constituency landscape in Wales, separate from UK parliamentary constituencies. In preparation for the May 2026 election, a boundary review took place which paired the existing thirty-two UK parliamentary constituencies in Wales to create sixteen new multi-member constituencies for the Senedd election. The new Senedd constituencies retained a link with the external boundaries of the Westminster constituencies through a statutory requirement (per Schedule 2 of the Act) that pairing ‘must consist of the combined areas of two contiguous UK parliamentary constituencies in Wales’. This requirement for retaining a contiguous link with UK parliamentary constituencies, however, does not apply to boundary reviews after May 2026 and is not included within the new constituency rules under the section 49C of the 2013 Act. Therefore, should the DMCC find in favour of redrawing the constituency map in Wales, the external boundaries of Senedd constituencies will diverge from those used at UK general elections.
Section 19: Reviewing the operation of the Act
As already outlined, the review provisions under section 19 require the relevant committee to consider two different elements of the Act’s effect. The first focusses on the substantive effect of Parts 1 & 2: this includes the Senedd and its Members, the number of Welsh Ministers, and the Senedd’s electoral system. Consulting the explanatory notes to the Act, the guidance on possible areas for inquiry into the effect of Parts 1 and 2 includes: (1) the impact of the new voting system on proportionality; (2) the introduction of multi-member constituencies; (3) and the experience of using closed lists.
The scope of this first element of section 19 covers some of the more controversial elements of the recent Senedd reforms, in particular the Closed Proportional List (CPL) electoral system. While the Special Purpose Committee on Senedd Reform (2022) recommended CPL, earlier reports by both the Expert Panel on Electoral Reform (2017) and the Committee on Senedd Electoral Reform (2020) rejected it as an option, citing the inability for voters to choose individual candidates, and the lack of accountability of individual members to voters. This inability to hold individual members to account has recently come under criticism, following the defection of Sarah Cooper-Lesadd MS from Reform to Plaid Cymru. The inability to hold to account such a radical shift in a Member’s political allegiance, less than six months after a Senedd election, raises questions of the accountability mechanisms under the new electoral system.
Controversially, the new CPL electoral system removes the possibility of by-elections. Instead, Members of a political party will be automatically replaced using party lists, if they vacate their seat during a Senedd term. Per section 11 GoWA, vacant seats are filled by the next candidate on the respective party list at the time of the Senedd election. In the case of a defection: if a Member is elected from the Party A list, defects to Party B during the Senedd term, then resigns, the vacant seat will be filled by the next candidate on the Party A list. This creates a system that is not only complex, but also removes the ability for voters to influence the composition of the Senedd between general elections.
The second element of section 19 reviews ‘the extent to which the elements of a healthy democracy are present in Wales’. By its very construction, this part of the review mechanism offers the possibility for broad terms of reference. This is especially the case as the Act does not define what constitutes the tenets of a ‘healthy democracy’. Instead, the Act’s explanatory notes detail the scope of this second review element as an inquiry into ‘any other Senedd reform issues’. Some indicative lines of inquiry on this theme are included in the explanatory notes: (1) the awareness and understanding of devolved Welsh government and elections; (2) an assessment of turnout levels and an exploration of proposals for how this may be increased; (3) support for members and parties to undertake their Senedd roles; (4) the infrastructure in place to support a strong Welsh democracy. The task for the committee under this second strand of section 19 will be to formulate terms of reference that are both measurable and deliverable within the limited timeframe of the review period.
Informing both strands of the section 19 review mechanism, the explanatory notes also propose that the committee should take into account the principles set down by the Expert Panel on Electoral Reform (2017): ‘such as proportionality, simplicity, and the extent to which the new system has delivered a Senedd that is reflective of the people of Wales.’ In its final report, the Expert Panel identified ten principles (para 10.02) against which to evaluate different electoral systems. While some of these will fall outside of the scope of the section 19 review, such as constituency boundaries, the Expert Panel’s principles relating to member accountability and voter choice will offer an interesting framework against which to evaluate the effectiveness of the new CPL electoral system.
The Time Available for Review
As discussed, the Act creates a time horizon of twelve months for the entire section 19 process to be completed. At the time of writing, there is under seven months until the reporting deadline of 12 May 2027. Factoring in the six weeks allocated for Senedd recess periods between now and the deadline, the time available to the review committee is less than six months. Compared to other recent Senedd reform investigations, this is a narrower review window: the Expert Panel on Electoral Reform (2017) reported after nine months; the Committee on Senedd Electoral Reform (2020) reported after twelve months; the Special Purpose Committee on Senedd Reform (2022) reported after seven months.
This narrow timeframe creates challenges for evidence gathering and the production of final recommendations. It also raises questions as to the Senedd’s intention when it passed the post-implementation review mechanism. Specifically, it is unclear why the Act creates different timeframes for review under sections 7 and 19. While both provisions include a six-month deadline for the Llywydd to table a review motion, only the section 19 mechanism includes a deadline for the committee to report its findings to the Senedd. Considering the Act was the culmination of two decades of deliberation, it is unclear why the Senedd passed such a narrow timeframe for analysing the Act’s operation and effect. A possible explanation lies in the new, reduced time limit of four years between Senedd elections, whereby a shorter review period would allow the committee’s report to affect further Senedd reforms before the next election in 2030. However, any procedural advantages that may be gained from time limits on the review period, stand to be offset by the limitations of reviewing the Act’s operation and effect within such a short timeframe, and so soon after a landmark Senedd election.
Outcomes: Further Senedd Reform?
Following publication of the committee’s final report, the Act (section 19(4)) requires the Welsh Ministers to lay a statement before the Senedd setting out their response. Neither the report, or the Welsh Minister’s response, require the instigation of a new tranche of Senedd reforms. However, given the controversial status of certain parts of the Act, namely the choice of electoral system, the question of further Senedd reform remains a salient issue in Welsh politics. This is confirmed by an examination of party manifestos from the May 2026 Senedd election: both Plaid Cymru and Welsh Liberal Democrats support the adoption of the Single Transferable Vote for Senedd elections; the Green Party supports a review of the current CPL system; and the Welsh Conservatives advocate reversing the increase to the number of Senedd members. This smorgasbord of proposals means that the review process attached to the section 19 motion (if passed by the Senedd), will feed into the ongoing political issue of further deliberations on Senedd reform.
In its 2026 Manifesto, Plaid Cymru committed to ‘work to build a cross-party majority for adopting the Single Transferable Vote (STV) for future Senedd elections’. As the largest party in the Senedd and leader of the Welsh government, Plaid Cymru are well placed to attempt to deliver this manifesto commitment. Securing the full range votes required to pass Senedd reform legislation will, however, be challenging for the government.
Per section 111A GoWA, amendments to the Senedd’s electoral system fall under the scope of a ‘protected subject-matter’ and so require a two-thirds majority in a plenary vote, in order to pass. During the Sixth Senedd, the Senedd reforms set out in the 2024 Act passed the two-thirds requirement with support from the minority Welsh Labour government and Plaid Cymru. Collectively, the two parties occupied 43 seats in the then 60 seat Senedd: meeting and exceeded the two-thirds threshold. Both parties had also already agreed to legislate for Senedd reform in the Co-operation Agreement (2021), and to support the Special Purpose Committee’s recommendations. That the Welsh Labour government was able to pass Senedd reform legislation while operating as a minority government during the Sixth Senedd, points to the success of its formal Co-operation Agreement with Plaid Cymru. Looking at the current Senedd, the threshold and seat share between the parties is more complex, and creates a far greater challenge for the government.
Following the Senedd’s increase up to 96 members after the May 2026 election, the two-thirds threshold now stands at 65 seats. At present, Plaid Cymru hold 44 seats in the Senedd and operate as a minority government: 5 seats short of an outright majority, and 21 short of the two-thirds requirement. To secure the 21 additional seats required to pass Senedd reform, Plaid Cymru have limited available options for political partners. Those ideologically proximate parties on the centre-left of Welsh politics (Welsh Labour, Lib Dems and Greens) collectively hold 12 seats and so cannot be relied upon to reach the two-thirds threshold. Instead, the threshold can only currently be achieved through an agreement between Plaid Cymru and Reform. As the Reform group currently holds 33 seats – just over a third of the Senedd seat share – they are the only viable partner to achieve the two-thirds threshold. Should Plaid Cymru decide to pursue a cross-party majority for STV, getting the Reform group to agree will be essential for the success of a Senedd vote.
Concluding Remarks
The provisions for post-implementation review of the operation and effect of the Act create new opportunities to revisit the debate on Senedd reform. Regarding the section 19 review mechanism, this blog has demonstrated how a review of the Senedd’s structural and electoral changes holds the potential for ambitious terms of reference: investigating the structural, procedural and normative effects of the Act on Welsh democracy. It has also demonstrated how the outcomes of the review process could feed into manifesto plans by the new Plaid Cymru government to affect further changes to the electoral system for future Senedd elections. It is now up to the Llywydd to introduce the review motion before the 12 November deadline and, if passed, for the Senedd to agree terms of reference that are both meaningful and deliverable within the narrow review timeframe.
My thanks to the editors for their helpful comments on an earlier draft of this blog.
Gareth Evans is a Lecturer in Law at Swansea University
(Suggested citation: G. Evans, ‘Revisiting Senedd reform: Post-implementation review of the Senedd Cymru (Members and Elections) Act 2024’, U.K. Const. L. Blog (22nd October 2026) (available at https://ukconstitutionallaw.org/))
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