Keir Starmer has announced Jeremy Corbyn will be barred from standing as a Labour candidate at the next election - over two years after removing the whip from the ex-leader.
His remarks came at a press conference on Wednesday - marking the end of the party being monitored by the Equality and Human Rights Commission over the issue of anti-Semitism.
The equalities body placed the party under special measures on its "day of shame" in October 2020 when it found Labour had committed unlawful acts.
The ex-Labour leader Mr Corbyn has had the whip suspended ever since over his response to the 130-page report. He has, however, had his membership of Labour restored.
Mr Starmer has been repeatedly asked about the issue over the last 24 months - but has only gone as far to suggest it is unlikely his predecessor will be given the whip back.
That changed on Wednesday as Mr Starmer told reporters: "Let me be very clear... Jeremy Corbyn will not stand for Labour at the next general election as a Labour candidate.
"What I said about the party changing, I meant.
"We're not going back and that is why Jeremy Corbyn will not stand as a Labour candidate at the next general election".
Mr Corbyn accused his successor of a "flagrant attack on the democratic rights" of Labour members in Islington North - a party stronghold in London he has represented since 1983.
In a statement, the left-wing MP added: "It's up to them - not party leaders - to decide who their candidate should be. 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".
Here The Mirror explores his options.
Continue to insist the Labour whip should be restored
The ex-Labour leader - who has previously insisted the whip was "wrongly" removed - has insisted he wants to stand as a Labour candidate at the next election.
The left-wing Momentum campaign group has also said: "It should be for Labour members in Islington North to decide their candidate - that is their democratic right".
Speaking on BBC Radio London, Mr Corbyn criticised the "poor" way his suspension from the Parliamentary Labour Party has been handled.
He added: "I am a member of the Labour Party, I attend meetings of my local Labour Party, I work with people in the local Labour Party and I campaign for them in the local elections. I will continue doing that."
In his statement this week he also indicated that despite Mr Starmer's comments he will still attempt to seek the Labour Party nomination in Islington North.
Mr Corbyn could continue pursuing this route until Labour HQ kicks off the formal process of stopping him from representing the party at the next general election.
This would likely involve opening the selection process for Labour's next candidate for Islington North - forcing the party to formally block the ex-Labour leader from standing.
The move would inevitably trigger a huge row with local Labour party members in the constituency and left-wing MPs who remain loyal to Mr Corbyn.
Announce decision to stand as an Independent
Mr Corbyn's close political ally in Parliament Diane Abbott - who served on his frontbench - said on Wednesday evening he had "no intention of standing as an independent".
But if he is blocked from standing for Labour by the party machine he may eventually decide his best chance of remaining the area's MP is to stand as an Independent at the next general election.
Given his longevity of service - 40 years - and his own personal popularity in the constituency he would also have a fighting chance of winning the seat in 2024.
But it would mean standing against the Labour Party candidate in Islington North and almost inevitably lead to his membership of the party being severed.
The division in one of Labour's safest seats in the country would play out as the party seeks its first election victory since 2005.
Local Party members and the left-wing campaign group Momentum would also have to decide whether to campaign for Mr Corbyn - a decision that could also lead to them losing their Labour membership.
Run for Mayor of London
In recent months there has been speculation that Mr Corbyn is being encouraged to make an attempt at running to become the next Mayor of London in May 2024.
A Corbyn ally told HuffPost UK last summer: "There are people who have encouraged him to run for Mayor.
"There are people who feel that given the Left's progressive agenda through some of the metro mayors, having Jeremy do something similar in London would be a good axis
"It's not something has has ever said he has an appetite to do, but it has been discussed by people close to him".
Previously Ken Livingstone failed to win the Labour nomination but went on to win the capital as an independent at the mayoral elections in 2020.
But it appears unlikely after the incumbent Labour Mayor Sadiq Khan announced in December he will seek a historic third term next year.
He said it would be used to "send a message to the Tories" over the dire state of the economy, adding: "There's still so much more to do".
Retire from Parliament
The ex-Labour leader could decide on none of the above options and decide after four decades in Parliament to retire from frontline politics.
He may announce he will not stand for Parliament at the next election - but continue campaigning for Labour in his capacity as a party member.
After resigning as leader of the Labour Party he also set up the Peace & Justice Project, which "brings people together for social and economic justice, peace and human rights in Britain and across the world".
He could decide to pursue his projects and causes close to him through this avenue rather than seeking re-election in Islington North.
In the final paragraph of his statement on Wednesday evening Mr Corbyn said: "I am focused on standing up for workers on the picket line, the marginalised, and all those worried about their futures. That is what I'll continue to do".
Whether he does that within Parliament after the next general election remains to be seen.
