Keir Mather is the Labour MP for Selby, having first been elected for the predecessor seat of Selby and Ainsty in a by-election on 20 July 2023.

In the 2024 general election, Mather won 22,788 votes, representing 46.3% of the vote. The Conservative candidate, Charles Richardson, received 12,593 votes (25.6%), while the Reform UK candidate, David Burns, secured 9,565 votes (19.4%). Mather was duly elected with a majority of 10,195 votes.

The Selby constituency was re-established for the 2024 election, primarily formed from the abolished Selby and Ainsty seat in North Yorkshire. It includes Selby, Sherburn-in-Elmet, and Kippax. The area was considered safe Conservative territory until the 2023 by-election.

Political Career

Mather was appointed to the post of parliamentary under-secretary of state in the Department for Transport in the September 2025 ministerial reshuffle. He served as an assistant government whip from July 2024 to September 2025.

Mather was an opposition whip from March 2024 to until the general election of that year.

Mather served on the House of Commons Treasury select committee from November 2023 to May 2024.

Mather is a patron of LGBT+ Labour – a socialist society formally affiliated with the Labour Party.

The 2023 Selby and Ainsty by-election was triggered by the resignation of Nigel Adams, the incumbent Conservative MPs. It was held alongside two further by-elections in Somerton and Frome, and Uxbridge and South Ruislip.

Boris Johnson had resigned as the MP for Uxbridge and South Ruislip in protest at the House of Commons privileges committee’s report into “Partygate”. The former prime minister had been given advanced sight of the report, which found he misled the House. Johnson stepped down as an MP rather than face a likely recall petition. Adams, a strong supporter of the ex-prime minister, resigned alongside Johnson in solidarity and protest.

In Selby and Ainsty, Labour and Mather achieved a historic victory. Mather overturned a Conservative majority of 20,137 from the 2019 general election, winning with a majority of 4,161 on a remarkable swing of 23.7% – one of the largest such swings to Labour from the Conservatives since the Second World War.

Aged 25 at the time, Mather became the youngest MP in the House of Commons. He therefore held the unofficial title of “baby of the House”.

Mather delivered his maiden speech on 16 October 2023 during a debate on Early Years Childcare.

In it, he said: “However, like so many other northern villages and towns, the success of communities in my constituency has been in spite of a government who have consistently failed to get the basics right.

“In our part of north Yorkshire, it is hard to stay healthy when a GP appointment or a timely ambulance is a thing of the past, and when dental provision is so poor that one resident told me that she had had to pull out one of her own daughter’s teeth.”

He added: “As young people, this is the future we choose. We are clear-eyed about the challenges that lie ahead but determined to play our part in realising our country’s promise. As I said on the night of my election, I hope to be a representative of that power of young people to make a difference.”

Political views

Mather voted in favour of the Terminally Ill Adults (End of Life) Bill, better known as the assisted dying bill, at both second reading (November 2024) and third reading (June 2025).

In a statement setting out his position, issued after the bill’s third reading, Mather commented: “I fully understand that this is one of the most important decisions I will make during in my time in Parliament – and I wanted to take the time to set out the reasons why, after much deliberation, I voted for this legislation at third reading.

“I have not arrived at this decision lightly and have done so after taking time to consider this highly complex ethical issue, alongside the precise wording of the bill itself.”

He added: “On the principle of the issue, I believe it is wrong that people with terminal illnesses who are near to the end of their natural lives do not have the ability to end their lives in a medically safe way.

“People should be able to avoid unspeakable pain, as well as physical and cognitive decline. Whilst they still have the agency, they should be able to make decisions about whether to end their lives if they find themselves in that position.”

Mather supported the Labour leadership’s policy of maintaining the two-child benefit cap in July 2023.

He stated at the time: “I think we’re going to inherit an absolute economic mess from the Conservatives when we take power and we’re going to have to make extremely difficult decisions once we do, and I support the Labour government in doing so.”

Welfare vote (July 2025): Mather supported the government’s flagship welfare bill at second reading. The vote came after ministers agreed to significant concessions to avoid defeat via a mass rebellion of Labour MPs on 1 July 2025.

Labour deputy leadership 2025: Mather was one of 175 Labour MPs who nominated Bridget Phillipson for the party’s deputy leadership in September 2025. The election followed the resignation of Angela Rayner, who stepped down as deputy prime minister and deputy party leader after an investigation into her tax affairs. It marked the first time since 2007 that Labour had held a deputy leadership contest while in government.

Phillipson, the serving education secretary, was widely viewed as the candidate favoured by Downing Street and the party leadership. She secured 175 nominations from the Parliamentary Labour Party (PLP), comfortably exceeding the 80 required to reach the final ballot. She was ultimately defeated by Lucy Powell.

Abortion decriminalisation (2025): Mather voted in favour of a backbench amendment to the Crime and Policing Bill that sought to decriminalise abortion in England and Wales in June 2025. The amendment, which was passed by a majority of 242 votes, removed women from the threat of prosecution for ending a pregnancy at any stage. As an issue of conscience, MPs were allowed to vote according to their personal beliefs.

Before Politics

Born Keir Alexander Mather in Kingston upon Hull on 29 January 1998.

He was born in Kingston upon Hull.

He attended South Hunsley school and was a member of the UK youth parliament.

He studied history and politics (BA, first class) at Wadham College, Oxford, and later gained a master of public policy (MPP) degree from University College, Oxford (Blavatnik school of government) as a political leadership scholar.

He worked as a researcher for shadow health secretary Wes Streeting MP from 2019 to 2020.

He then worked as a public affairs adviser for the Confederation of British Industry (CBI) until his selection as a parliamentary candidate in 2023.

Personal Life

Mather reportedly lives in Selby.

In 2024, PinkNews listed Mather among a number of out LGBTQ+ parliamentarians.

Trivia

Mather is named after Labour founder Keir Hardie.

He supports the Rugby League team Hull KR.