Keir Starmer has told his critics in the Labour party to back him or quit - and said the party is "never going back".
The Labour leader said the party was "unrecognisable" from when he took over from Jeremy Corbyn and the changes he's made are “permanent, fundamental, irrevocable”.
In a direct challenge to Mr Corbyn's backers, he said: “There are those who don’t like that change, who still refuse to see the reality of what had gone on under the previous leadership.
"To them I say in all candour: we are never going back. If you don’t like it, nobody is forcing you to stay."
It comes as the equalities watchdog announced that Labour was no longer in special measures over the wave of anti-Semitism allegations that gripped the party during Mr Corbyn's tenure.
The Equalities and Human Rights Commission (EHRC) said it was no longer monitoring the party following Labour's "day of shame" in October 2020 when it found the party had breached the Equality Act.
Mr Starmer will apologise again on behalf of the party at a speech in London this morning.
In an article in the Times, he said the work of reforming Labour was not over and said any members with doubts about the need for change should leave.
"From the moment I was elected Labour leader I was clear about what we needed to do to rebuild our party," he said.
"Not only had we lost an election badly, we had also lost sight of our morals and our purpose."
Mr Starmer said rooting out anti-Semitism was the most pressing issue in his in-tray when he took over as Labour had become "an incubator for this poison".
He said the EHRC decision was a key moment but the job was not done - and instead was a moment for reflection.
The Labour leader promised to root out prejudice of all kinds and to "bring this party back to the British people".
"The changes we have made aren’t just fiddling around the edges or temporary fixes," he said.
"They are permanent, fundamental, irrevocable.
"The Labour Party I lead today is unrecognisable from 2019.
"There are those who don’t like that change, who still refuse to see the reality of what had gone on under the previous leadership. To them I say in all candour: we are never going back."
In a swipe at his predecessor, he said: "The Labour Party I lead is patriotic.
"It is a party of public service, not protest. It is a party of equality, justice and fairness; one that proudly puts the needs of working people above any fringe interest."
The fate of Mr Corbyn is hanging over the Labour leader as pressure mounts on the party to select a candidate in the former leader's Islington North seat.
Mr Corbyn has been readmitted to the Labour Party after he was suspended in October 2020 for suggesting complaints of anti-Semitism had been "dramatically overstated".
But Mr Starmer has refused to restore the whip, meaning Mr Corbyn still sits as an independent MP.
The Labour leader must decide whether to select a Labour candidate to contest the seat or readmit Mr Corbyn ahead of the next election.
Labour MP Dame Margaret Hodge, who was a vocal critic of Mr Corbyn, said he was unlikely to be allowed to stand for the party.
She told BBC Radio 4 Today: "I cannot think of any circumstances whatsoever under which Jeremy could stand as a candidate for the Labour Party at the next general election.
"He's been a master of his own destiny, he knew what he did in the past, he knew what he did when the EHRC came out and he's only got himself to blame.
"I've moved on from Corbyn, the party has definitely moved on from Corbyn, the country's moved on from Corbyn if you see what Labour is gaining now in the polls and I think Corbyn is just part of the past, he's a relic of yesterday."
Mr Corbyn has made it clear he wants to stand again in the seat he has held for nearly 40 years.
He told the Standard last month: “I have been clear that the whip was wrongly removed, and it should be restored.
"So, too, should the democratic rights of local Labour party members, who must be allowed to choose who represents them in Parliament."
