Sir Keir Starmer has for the first time unequivocally barred his predecessor Jeremy Corbyn from standing as a Labour candidate at the next general election as he invited his critics to leave the party.

On an “important day” for Labour, Sir Keir welcomed the equalities watchdog’s decision to lift the party out of two years of special measures over its past failings on antisemitism.

He used a speech on Wednesday to invite his opponents on the Labour left to leave the party which he said is now “unrecognisable” from its form under Mr Corbyn.

“Let me be very clear, Jeremy Corbyn will not stand at the next general election as a Labour Party candidate,” Sir Keir said in east London.

“What I said about the party changing I meant and we are not going back.”

Mr Corbyn will speak to Labour members in his Islington North constituency before deciding his next steps, the PA news agency understands.

But his allies expect Sir Keir to have the powers to prevent any challenge for the candidacy against the leadership’s wishes.

The Equality and Human Rights Commission (EHRC) had been monitoring Labour since ruling in 2020 that it was responsible for unlawful acts of harassment and discrimination under Mr Corbyn.

But on Wednesday the watchdog judged that, under Sir Keir, Labour has improved its complaints and training procedures to protect current and future party members.

Mr Corbyn was suspended from the parliamentary party over his response to EHRC’s damning report in 2020 and now sits as an independent MP.

Sir Keir has long indicated that Mr Corbyn will not stand again for Labour but this is the first time he confirmed the barring of the veteran who led the party to two election defeats.

If Mr Corbyn decides to run as an independent candidate for the constituency he has represented for 40 years, Labour would come up against his personal popularity in Islington North as well as a potentially distracting row with the left-winger.

Sir Keir reiterated his vow that anyone who plays down antisemitism will be treated with “zero patience or tolerance” and acknowledged it is not “the end of the road” for tackling the issue.

“I understand that some people won’t like the changes we’ve made but I say this with all candour, the Labour Party is unrecognisable from 2019 and it will never go back,” he said.

“It will never again be a party captured by narrow interest, it will never again lose sight of its purpose or its morals. And it will never again be brought to its knees by racism or bigotry.

“If you don’t like that, if you don’t like the changes we’ve made, I say the door is open and you can leave.”

Asked whether he will now proscribe the Corbyn-backing Momentum campaign, Sir Keir said he does not have the power to take that action but reiterated his open-door policy to opponents.

Momentum responded: “It should be for Labour members in Islington North to decide their candidate – that is their democratic right.”

Sir Keir was introduced to the podium in Toynbee Hall by the president of the Board of Deputies of British Jews, Marie van der Zyl.

She said the idea of addressing the audience before the Labour leader “not too long ago” would “simply would be an impossibility”.

“At the next election I believe all British Jews will once again be free to vote according to their political persuasion rather than out of fear,” she said.

However, she offered a “note of caution” that there are still “issues with antisemitism, particularly within the grassroots” of the Labour Party.

The EHRC’s damning investigation published in October 2020 found evidence of “political interference” by Mr Corbyn’s office in the complaints process.

The watchdog said there had been “inexcusable” failures which “appeared to be a result of a lack of willingness to tackle anti-Semitism rather than an inability to do so”.

Mr Corbyn claimed the scale of the problem had been “dramatically overstated for political reasons by our opponents inside and outside the party, as well as by much of the media”.

On Wednesday the EHRC announced that its action plan for Labour to address breaches of the Equality Act concluded at the end of January and it was satisfied with the reforms.

Among the watchdog’s demands were for Labour to commit to zero-tolerance of antisemitism and to set up an independent complaints handling process.

Consultation over the reforms had to include the Jewish community, social media guidelines had to be tightened and due diligence checks had to be strengthened on candidates.