Sir Keir Starmer was urged to let Diane Abbott back into Labour ranks in Parliament after he welcomed Tory defector Natalie Elphicke.
Baroness Shami Chakrabarti stressed that the Tories and Labour had both traditionally been “broad church” parties.
The former shadow Attorney General and ex-director of human rights group Liberty, said: “You measure the breadth of the church from one wall to the other.
“So what I would say is...if there is now a place for a changed Natalie Elphicke in the Parliamentary Labour Party, surely my friend Diane Abbott will have the whip restored quick smart.
“That is something I should be able to look forward to in this context of a broad church.”
Sir Keir has faced fury from some Labour MPs over his decision to welcome Dover MP Ms Elphicke into the Labour Party.
She has criticised Labour’s policy on immigration and was condemned for remarks she made supporting her ex-husband after he was convicted of sexual assault.
She apologised on Thursday for the comments as Labour sought to defuse the row over her defection.
Ms Elphicke's former husband and predecessor as MP for Dover, Charlie Elphicke, was convicted in 2020 of sexually assaulting two women and jailed for two years.
She ended the marriage after his conviction but supported his unsuccessful appeal, saying Mr Elphicke had been "attractive, and attracted to women" and "an easy target for dirty politics and false allegations".
In a statement on Thursday, Ms Elphicke said she condemned "his behaviour towards other women and towards me", adding it was "right that he was prosecuted" and she was "sorry for the comments that I made about his victims".
Few Labour MPs have spoken out publicly to criticise the decision to allow the former Tory MP onto the Labour benches.
But former Labour leader Lord Kinnock said: “We have got to be choosy to a degree about who we allow to join our party because it's a very broad church but churches have walls and there are limits.”
Privately, Labour MPs were withering in their criticism of the decision to accept Ms Elphicke into the party but still to refuse to return the parliamentary whip to Ms Abbott, Britain’s first black MP.
One senior Labour MP said: “This is outrageous.
“Labour MPs are incredulous about what has happened.”
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On accepting Ms Elphicke into the party, he added: “Politics is about policies and values and this does not conform with our policies or our values.
“It just debases politics.”
Another Labour MP criticised welcoming the defection of the Dover MP to the party but still refusing to allow Ms Abbott, veteran MP for Hackney North and Stoke Newington, to return to the parliamentary party.
“Both of them require a process and it’s not clear that the process for Diane has been moving forward any more than it’s clear that a process of vetting Natalie on her views on sexual harassment and refugees has been conducted,” said the MP.
Ms Abbott was suspended from the parliamentary Labour party last April for appearing in a letter to the Observer to diminish racism against Jewish people.
She withdrew her remarks and apologised "for any anguish caused" but still remains outside the parliamentary Labour party.