Diane Abbott today lashed out at Sir Keir Starmer for welcoming Tory defector Natalie Elphicke to Labour while she herself remains suspended from the party.
The veteran left-winger, who has been MP for Hackney North and Stoke Newington since 1987, has had the Labour whip withdrawn for more than a year.
She was suspended amid a probe into her comments about Jewish people in a letter to the Observer newspaper in April last year.
Ms Abbott issued a swift apology for her remarks, in which she suggested Jewish, Irish and Traveller people experience 'prejudice' but are not 'subject to racism'.
But she is still having to sit as an independent MP in the House of Commons as the long-running investigation continues.
The former shadow home secretary drew a comparison between her own treatment by Labour and that of Ms Elphicke, whose defection has sparked a party backlash.
Ms Abbott said Ms Elphicke was 'right to apologise' for past comments in which she appeared to blame victims after her husband Charlie Elphicke, whom she succeeded as Dover MP, was convicted of sexual assualt.
But, in a swipe at Sir Keir, Ms Abbott added: 'The decision to accept it five years after she first said it is unusual. Not everyone is treated with such generosity.'
Sir Keir this morning defended dismissed anger in his own ranks at Ms Elphicke being allowed to join Labour and claimed politics should be 'less tribal'.
Diane Abbott lashed out at Sir Keir Starmer for welcoming Tory defector Natalie Elphicke to Labour while she herself remains suspended from the party
Ms Elphicke joined Sir Keir in her Dover constituency this morning to launch Labour's plans to tackle people-smuggling gangs bringing migrants across the Channel in small boats
Ms Abbott drew a comparison between her own treatment by Labour and that of Ms Elphicke, whose defection has sparked a party backlash
Labour MPs have criticised the decision to admit Ms Elphicke to the party, citing her hardline views on immigration and past support of her ex-husband.
The Dover MP apologised yesterday for claiming after Charlie Elphicke's 2020 conviction that he was 'attractive, and attracted to women' and 'an easy target for dirty politics and false allegations'.
She said: 'The period of 2017 - 2020 was an incredibly stressful and difficult one for me as I learned more about the person I thought I knew.
'I know it was far harder for the women who had to relive their experiences and give evidence against him.'
Jess Phillips, the former shadow minister for domestic violence and safeguarding, had earlier said Ms Elphicke should 'account for her actions', adding: 'I'm all for forgiveness but I do think that that needs some explaining.'
Ms Elphicke stunned Westminster by crossing the floor of the Commons to sit on Labour's benches just ahead of Prime Minister's Questions on Wednesday.
She joined Sir Keir in her Dover constituency this morning to launch Labour's plans to tackle people-smuggling gangs bringing migrants across the Channel in small boats.
Speaking at the event, Sir Keir dismissed anger in his own ranks at Ms Elphicke being allowed to join the party.
He argued that Ms Elphicke's switch showed 'we've got a Tory party that is on its last legs... it's out of ideas' and urged people to be 'less tribal in our pursuit of a better country'.
Sir Keir said: 'I'm very pleased to welcome Natalie to the Labour Party. You've heard the reasons yourself why she took that very difficult step.'
The Labour leader added he wanted his party to be a place that 'reasonably-minded people, whichever way they voted in the past' feel they can join.
'It is an invitation that we should be less tribal in the pursuit of a better country and invite people to our party who want to join in our object of national renewal,' he said.
Shadow health secretary Wes Streeting has boasted that Labour is talking to more prospective switchers on the Tory benches, with Dan Poulter already having made the change a fortnight ago.
But critics have accused Sir Keir of turning the party into a 'dustbin' for Conservative right-wingers - while even normally staunch supporter Lord Kinnock has warned Sir Keir needs to be careful who to accept.
Labour frontbencher Lisa Nandy suffered an awkward moment on the BBC's Question Time last night when the audience was asked whether Ms Elphicke was an 'asset' to her party and no-one put their hand up.
Asked if he was concerned about the backlash from within the Labour Party to Ms Elphicke's defection, Starmer said today that she had set out the reasons for this 'very important and significant' defection.
He said: 'It's a Conservative Party that is on its last legs, it's out of road, out of ideas, and that is why I genuinely think the mood of the country, and Natalie has picked up on this, is for change and a general election.'
No-one can understand why Mr Sunak is 'clinging on by his fingernails' to power, Sir Keir added.
Ms Elphicke stunned Westminster this week when she switched sides from the Conservatives to Sir Keir's Labour just before Prime Minister's Questions on Wednesday
Downing Street has pointed out Ms Elphicke's past attacks on Labour's immigration policy while former prime minister Lord Cameron said her defection showed the opposition stood for nothing.
There were calls for Ms Abbott to be readmitted as a Labour MP earlier this year after she was put at the centre of a Conservative racism scandal.
Tory donor Frank Hester was reported to have said Ms Abbott, Britain's first black female MP, made him 'want to hate all black women' and that she 'should be shot'.
Labour deputy leader Angela Rayner branded the comments about Ms Abbott as 'absolutely chilling' and said she 'would like to see' the veteran MP's suspension lifted.
Ms Abbott was accused of 'spouting hateful anti-Semitism' with her newspaper letter in April last year.
The row was sparked by her response to a comment article that stated Irish, Jewish and Traveller people all suffer from racism.
'They undoubtedly experience prejudice,' Ms Abbott wrote.
'This is similar to racism and the two words are often used as if they are interchangeable.
'It is true that many types of white people with points of difference, such as redheads, can experience this prejudice.
'But they are not all their lives subject to racism. In pre-civil rights America, Irish people, Jewish people and Travellers were not required to sit at the back of the bus.
'In apartheid South Africa, these groups were allowed to vote. And at the height of slavery, there were no white-seeming people manacled on the slave ships.'
Amid the backlash against her comments, Ms Abbott issued a public apology.
In a statement posted on her Twitter account, she wrote: 'I am writing regarding my letter that was recently published in the Observer.
'I wish to wholly and unreservedly withdraw my remarks and disassociate myself from them.
'The errors arose in an initial draft being sent. But there is no excuse and I wish to apologise for any anguish caused.
'Racism takes many forms, and it is completely undeniable that Jewish people have suffered its monstrous effects, as have Irish people, Travellers and many others.
'Once again, I would likely (sic) to apologise publicly for the remarks and any distress caused as a result of them.'