MP Ian Austin quits Labour, accusing Jeremy Corbyn and John McDonnell of supporting the IRA

Mr Austin, the ninth MP to quit Labour in a week, claimed there was a “culture of extremism, anti-Semitism and intolerance” within the party.

He said he is “ashamed” of the party under Jeremy Corbyn’s leadership and “appalled” by the offence it has caused to Jews.

The Dudley North MP, whose Jewish adoptive father was forced to flee the Nazis as a child, said he joined Labour to fight racism and “I could never have believed that I’d be leaving because of racism too”.

He said he could never ask his constituents to make Mr Corbyn prime minister, claiming the Labour leader and shadow chancellor John McDonnell supported the IRA and “cannot be trusted with our national security and would undermine our democratic institutions”.

A Labour Party spokesperson declined to respond to the specific claims made by Mr Austin alleging that Mr Corbyn and Mr McDonnell supported the IRA, but did say: “We regret that Ian Austin has left the Labour Party. He was elected as a Labour MP and so the democratic thing is to resign his seat and let the people of Dudley decide who should represent them.”

Khalid Mahmood, Labour MP for Birmingham Perry Barr, called Mr Austin’s decision to quit the party “very sad”.

He told the Press Association: “I’ve known Ian a long time, before we were MPs and he has been a good friend. It’s regrettable that he’s done this.”

He added that Labour under Mr Corbyn was “doing its best” on anti-Semitism, and was operating a “zero-tolerance” policy on the issue.

He said: “Unfortunately there are those associated with the party who make comments.

“But the party is doing its best and will continue to have zero tolerance against anti-Semitism.”

Mr Austin said he has no plans to join his eight former colleagues in the new Independent Group they had set up this week.

He announced his decision in his local newspaper, the Express & Star, and issued a fuller explanation in a statement on his website.

Referring to Mr Corbyn, he said: “I always thought he was unfit to lead the Labour Party and I certainly think he is unfit to lead our country.”