Kim Leadbeater sworn in as the new MP for Batley and Spen.

Kim Leadbeater and Labour leader Sir Keir Starmer celebrate with supporters in Cleckheaton after her victory in the Batley and Spen by-election. Photo: Getty Images

Ms Leadbeater was welcomed to the House of Commons for the first time by many Labour MPs who had filled the Commons benches, including party leader Sir Keir Starmer

The seat was previously held by her sister Jo Cox, who was murdered in the constituency in June 2016.

There was applause from the opposition benches when a grinning Ms Leadbeater gave a thumbs up after she took the oath in front of the Speaker of the House of Commons, Sir Lindsay Hoyle.

She was elected with a majority of just 323 votes last Thursday, beating the Conservative candidate Ryan Stephenson, whom many had predicted to win.

She took 13,296 votes compared to Mr Stephenson’s 12,973, while George Galloway came in third with 8,264 votes.

It followed a campaign marked by accusations of violence and dirty tricks as Labour supporters and Mr Galloway’s Workers Party battled for votes in the constituency.

Speaking after she was announced as the new MP in the early hours of Friday morning, Ms Leadbeater said: “I’m absolutely delighted that the people of Batley and Spen have rejected division and they’ve voted for hope.”

The result was also celebrated by Labour leader Sir Keir Starmer, calling it a “fantastic result" for the "brilliant and brave” Ms Leadbeater.

“Kim ran a positive campaign of hope in the face of division” he said.

“She will be an outstanding Labour MP for Batley and Spen.”