Keir Mather entered Parliament through the Selby and Ainsty by-election in July 2023, overturning a Conservative majority of more than 20,000. He retained the redrawn Selby constituency at the 2024 general election with 22,788 votes and a majority of 10,195.

Labour appointed him an assistant government whip on 10 July 2024. The role placed him inside the operation responsible for maintaining Commons discipline and passing government legislation, but gave him no department or policy programme of his own.

He became parliamentary under-secretary at the Department for Transport on 7 September 2025. His responsibilities covered aviation, maritime policy, electric vehicles, transport decarbonisation, freight and borders.

Mather retained a transport post after the change of government leadership in July 2026. That continuity showed political confidence in him, although he remained a junior minister working beneath the transport secretary.

What he stands for

Mather's ministerial politics combine support for economic growth with government-directed transport decarbonisation. He has backed subsidies, regulation and public investment to increase the use of electric commercial vehicles, cleaner shipping and sustainable aviation fuel.

In March 2026, his department announced £1 billion for electric vans, lorries and depot charging. The package was intended to reduce the additional cost faced by businesses replacing diesel vehicles and to expand charging infrastructure for commercial fleets.

He also supported government intervention to create a British sustainable aviation fuel industry. The Sustainable Aviation Fuel Act 2026 established powers for a revenue-certainty mechanism intended to provide producers with more predictable returns. The Act received Royal Assent on 5 March 2026.

His approach accepts continued aviation growth while attempting to reduce its carbon intensity. The government simultaneously promoted sustainable fuels and advanced a planning framework for a third runway at Heathrow. A public consultation on the revised Heathrow expansion policy opened in June 2026.

That position relies on technological improvement and cleaner fuel rather than reducing demand for flying.

What he actually delivered

The Sustainable Aviation Fuel Act was Mather's strongest completed legislative result as a minister. The legislation created the statutory machinery needed for contracts designed to protect producers from unpredictable differences between sustainable and conventional fuel prices.

Credit must be shared. The bill was government legislation sponsored formally by the transport secretary in the Commons and Lord Hendy in the Lords. The policy also developed from powers and consultation requirements contained in the Energy Act 2023, before Mather became a minister.

Mather subsequently announced £219 million for low-carbon fuel development, including £93 million immediately available for companies seeking to expand sustainable aviation fuel production. Claims that the wider programme could support 15,000 jobs and add £5 billion to the economy by 2050 were forecasts, not completed results.

In maritime policy, he announced £271 million for cleaner vessels, port infrastructure and maritime technology as part of a wider £448 million commitment. The funding was allocated, but the ships had not all been converted and the projected employment and emissions benefits had not been measured.

His proposals to strengthen pay, rest periods and employment protection for seafarers remained under consultation. They were not yet enacted rights.

Capability judgement

Mather has proved that he can handle a broad technical brief, defend government policy and help carry a specialised Act into law. His rapid movement from the whips' office to transport ministry was supported by evidence of reliability and command of detail.

His practical record is less developed. Much of his programme consisted of grants, consultations and predicted economic benefits. The sustainable-fuel legislation created a financing mechanism, but did not itself produce a functioning domestic industry at the scale ministers promised. Electric freight support was funded, but the transition of commercial fleets remained incomplete.

The evidence supports Mather as a capable junior minister and legislative operator. It does not yet show that the large sums and regulatory frameworks he announced produced lasting reductions in transport emissions or commercially successful new industries.