The Labour Party candidate Keir Mather has won a record victory over the Conservatives in the Selby and Ainsty by-election, in the highest majority the party has ever overturned in by-election history.

It marks the first time Labour has ever won the seat, with a majority of 4,161 on a 41.9% turnout. One party source said that if Labour won seats requiring a similar swing at a general election, it would win more seats than in 1997.

In Mather’s victory speech, he said he had seen so much “hardship” in the constituency during his campaign, with voters highlighting the cost-of-living squeeze, and pledged to ensure change.