Jeremy Corbyn was told by senior Labour MP Yvette Cooper on Thursday that he will lose the Islington North General Election contest if he stands as an independent.
Asked on BBC Radio 4’s Today programme if the ex-leader stands as an independent in the north London seat whether Labour could beat him, shadow home secretary Ms Cooper said: “I think so.
“The issue is that the Labour Party has changed.”
Former Cabinet minister Ms Cooper added: “Keir has made very clear that we have changed. We have come a very long way since 2019.
“That is the result of Keir’s leadership and I pay tribute to that because that was a really difficult period for the Labour Party.
“We must never go back there.”
She also stressed: “Keir Starmer has made it really clear.
“The party has moved on from the awful stain of anti-Semitism that we had and Keir expected everybody to take action to meet the new standards.”
Mr Corbyn has attacked Sir Keir's decision to bar him from standing as a Labour candidate at the next election as a "flagrant attack" on democracy.
The former Labour leader, who currently sits as an independent MP, hit out at his successor - describing the move as a "divisive distraction from our overriding goal: to defeat the Conservative Party".
It comes after Sir Keir for the first time unequivocally barred Mr Corbyn from standing as a Labour candidate at the next General Election.
The Labour leader also welcomed the Equality and Human Rights Commission's decision to lift the party out of two years of special measures over its past failings on anti-Semitism.
Responding to Sir Keir, Mr Corbyn added: "Any attempt to block my candidacy is a denial of due process, and should be opposed by anybody who believes in the value of democracy."
His close ally Diane Abbott, MP for Hackney North and Stoke Newington, does not believe he will stand as an independent.