Jeremy Corbyn will not stand as a Labour MP at the next election, Keir Starmer has said, as he vowed to paint his party as one that has changed under his leadership.

Starmer had previously publicly indicated that Corbyn would not be able to stand as a Labour candidate, but had not gone as far as confirming the barring of the Islington North MP.

“Let me be very clear, Jeremy Corbyn will not stand at the next general election as a Labour party candidate,” Starmer said on Wednesday while answering questions after a speech in east London. “What I said about the party changing, I meant, and we are not going back, and that is why Jeremy Corbyn will not stand as a Labour candidate at the next general election.”

The Labour leader was speaking as he marked an “important moment” for Labour after the Equality and Human Rights Commission (EHRC) lifted the party out of special measures over its past failings on antisemitism.

In a clear mark of his growing confidence, Starmer also invited Labour MPs who have long supported Corbyn to leave the party if they did not agree with his stance on driving out antisemitism.

Corbyn led the party for nearly five years, and has been supported by Momentum since his 2015 leadership campaign. If he decided to run at the next election as an independent, it would pose a potentially existential dilemma for the grassroots group.

Asked whether he would put Momentum “on notice”, Starmer said: “Well, I have many powers and duties and responsibilities in the Labour party, but that one is not for me, I’m afraid. But look, whatever group or individual in the Labour party, I think the message from this morning couldn’t be clearer.

“This is an important day. It’s a day of reflection. The change that we brought about is substantial and it is permanent. The Labour party has changed. And if there’s anyone in the Labour party that does not like that change, then my message to them is very clear this morning: the door is open, and you can leave.”

Allies of the former Labour leader have previously signalled he will run again for his Islington North seat regardless of whether he has the whip restored. One said local people respected him for his work in the constituency.

A Momentum spokesperson said on Wednesday: “Labour is a democratic socialist party – it’s written on our membership cards. This party does not belong to one man alone – it belongs to its members and trade unions.

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

Labour party officials are said to be looking for a strong candidate in the constituency, which Corbyn has held since 1983. “The local party is likely to be difficult and the campaign will be very tough if Jeremy stands as an independent,” a source told.