The Labour Party has won Selby and Ainsty from the Conservatives in the largest Tory majority overturned at a by-election.
Labour’s Keir Mather won the seat in North Yorkshire with 16,456 votes.
The Conservative Party candidate Claire Holmes received 12,295 votes and the Lib Dems Matt Walker came in third with 1,188.
Labour has overturned its biggest-ever majority of 20,137 at a by-election.
The result means Mr Mather, 25, has become the youngest MP at Westminster.
In his speech after being declared the winner of the Selby & Ainsty by-election, Labour’s Keir Mather said he “understood the enormity of what has just happened”.
He said: “We have rewritten the rules on where Labour can win. People have opened their doors to us and embraced our positive vision for the future.
“The people of Selby and Ainsty have sent a clear message. For too long, Conservatives up here and in Westminster have failed us, and today that changes.
“Over the past few months, speaking to hundreds of people on the doorstep, I’ve encountered so much hardship. Hardship made worse by 13 years of negligence and complacency from the Conservatives.”
Labour leader Sir Keir Starmer said: “This is a historic result that shows that people are looking at Labour and seeing a changed party that is focused entirely on the priorities of working people with an ambitious, practical plan to deliver.
“Keir Mather will be a fantastic MP who will deliver the fresh start Selby and Ainsty deserves.
“It is clear just how powerful the demand for change is. Voters put their trust in us — many for the first time.
“After 13 years of Tory chaos, only Labour can give the country its hope, its optimism and its future back.”
This story is being updated.