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Senedd Cymru (Members and Elections) Act 2024

The Senedd Cymru (Members and Elections) Act 2024 (“the Act”) delivers the majority of the recommendations made by the Senedd’s Special Purpose Committee on Senedd Reform. The Committee’s report: Reforming our Senedd: A stronger voice for the People of Wales was published in May 2022 and included recommendations on reforming the Senedd ahead of the Senedd elections in 2026. 

The Act: 

  • increases the number of Members of the Senedd from 60 to 96 by amending the number of constituencies and the number of seats for each constituency;
  • makes associated changes including increasing the legislative limit on the number of Welsh Government Ministers and the maximum number of Deputy Presiding Officers who may be elected from within the Senedd;
  • changes the Senedd’s electoral system so that all Members are elected via a closed proportional list system, with votes translated into seats via the d’Hondt formula (see below); 
  • repurposes and renames the Local Democracy and Boundary Commission for Wales to become the Democracy and Boundary Commission Cymru, with the functions necessary to establish and undertake ongoing reviews of Senedd constituency boundaries; 
  • provides instructions for the Democracy and Boundary Commission Cymru to follow when undertaking their boundary reviews. The instructions are for the initial streamlined review to pair the new 32 UK Parliamentary constituencies in advance of the 2026 Senedd election to form 16 new Senedd constituencies; 
  • contains further instructions for a full boundary review in advance of the election after 2026 and for ongoing periodic reviews;
  • decreases the length of time between Senedd ordinary general elections from 5 to 4 years; 
  • requires that Senedd candidates and Members are registered to vote in local government elections in Wales (which requires them to be resident in Wales); 
  • allows the Senedd to establish a committee to review of the operation of the new legislative provisions following the 2026 elections; and 
  • allows the Senedd to establish a committee to review job sharing for candidates standing in a Senedd election and Members holding particular roles, as well as temporary cover for particular roles.

The Explanatory Notes to the Act provide detailed commentary on the various provisions.

Coming into force

The Act comes into force as follows, in accordance with section 25:

  • Part 3, section 17, Part 5 (other than section 20) and Schedule 2 come into force on the day after the Act receives Royal Assent (namely 25 June 2024); 
  • sections 1, 2, 6, 7, 18, 19, 21, Part 2 and Schedule 3 come into force two months after the day the Act receives Royal Assent (namely 24 August 2024); 
  • section 3 comes into force the day after the day of a poll for the first general election held after 7 November 2025; 
  • sections 4 and 5 come into force the day after the day of a poll for the first general election held after 6 April 2026.

Consideration of the legislation by the Senedd

The Bill was introduced to the Senedd on 18 September 2023 by Mick Antoniw MS, who was the Counsel General and Minister for the Constitution at the time. It was passed by the Senedd on 8 May 2024 and received Royal Assent on 24 June 2024.

More information about the Act is provided on the Senedd website including a record of the Bill’s passage through the Senedd.

The Explanatory Memorandum that was prepared by the Welsh Government to accompany the Bill has been updated following Royal Assent.

Related articles and information

  • Senedd Research produced this Bill Summary to explain the proposals contained in the Senedd Cymru (Members and Elections) Bill. 
  • This page has more information on the Welsh Government’s plans to create a more effective and representative Senedd:  Senedd reform | GOV.WALES
  • Further background information is also available here: Senedd Reform: What Is It? (And Other Questions!); Senedd reform – the story so far.
  • The d’Hondt method is a mathematical formula used worldwide in various electoral systems, including for regional seats in the current Senedd. It is named after Belgian lawyer and mathematician, Victor d’Hondt, who developed it in the 1880s as an attempt to better accommodate different linguistic groups and political traditions in the Belgian parliament.


    The method assigns seats or positions based on the proportion of votes each party receives in an election. It does this by repeatedly calculating a quotient for each party and giving the next seat or position to the party with the highest quotient. This enables power to be distributed among parties according to their size.


    Under the formula, the number of votes cast for each party is divided by the number of seats the party has already won, plus 1. For example, if a party has won 2 seats, the number of votes won is divided by 3. The party with the highest number of votes each round wins the seat, and this is repeated until all seats have been filled.


Published on
Last updated
09 July 2024