Former foreign secretary David Miliband has told Sophy Ridge on Sunday it is "shameful" to have been found "colluding… in what is essentially racist behaviour" when asked about Labour's antisemitism report.
He said: "You can't think of anything more shameful really than to be found to be colluding, conniving in what is essentially racist behaviour or actions.
"So this is painful, this is shameful, as [leader] Keir Starmer said, I think he used that word, for every member of the Labour Party and it's a stain that has to be erased with absolute drive and determination."
Jeremy Corbyn was suspended from Labour on Friday after saying complaints of antisemitism in the party were "overstated", in a damning report by the Equality and Human Rights Commission (EHRC).
The report concluded the party broke the law in its failure to handle antisemitism complaints and that there were "serious failings" by its leadership.
Mr Miliband, who is now chief executive of the International Rescue Committee, told the show it was "definitely" right that Mr Corbyn had been suspended from the party, and that the former Labour leader's response "showed all of the blindness, all of the arrogance, all of the sticking of your fingers in your ears that we'd seen in his time as leader".
He accused Mr Corbyn of having "suspended himself", and "put himself beyond the pale".
Speaking from his home in New York, the former Labour minister told Sky News the issue extended to other members of the "hard left".
He said: "I've always been more on the centre-left and I've had disagreements with those on the hard-left but never in my worst thoughts did I think that the hill that they would choose to fight on would be the hill of anti-Semitism.
"I mean, they put themselves beyond the pale and I think the hard questions frankly are for them."
Speaking about the party's history, Mr Miliband said Mr Corbyn was "never going to be elected as prime minister".
"If you have a candidate who attracts people, you can win elections and put your values into practice.
"If you have a candidate like Jeremy Corbyn who repels voters, you've got no chance of being able to put your values into practice and that is the tragedy of British politics over the last 10 years."
He criticised President Trump, saying he had made no progress engaging with North Korea or China and that Iran is closer to a nuclear weapon than four years ago.
He added: "When it comes to engagement with China, obviously American farmers and consumers have paid the price of the tariffs that have come in and China is actually in a much stronger position today than it was four years ago."