Mr Corbyn was reinstated as a member of the party yesterday, three weeks after he was suspended for his response to a damning Equality and Human Rights Commission (EHRC) report into anti-Semitism in the Labour Party.
Sir Keir was today under pressure from moderate MPs to keep his predecessor out of the parliamentary party while risking a revolt from the left of the party.
Marie van der Zyl, president of the Jewish Board of Deputies, told BBC Radio 4’s Today Programme: “I think the decision to reinstate Jeremy Corbyn is an absolute sham.
Watch: Keir Starmer questioned over Corbyn's Labour return
“Jeremy Corbyn’s case has clearly been rushed through and judged by a politicised panel stuffed with his own supporters.”
She said she hoped Sir Keir would make it clear he would not restore the whip and added: “Jeremy Corbyn is a man who has allowed anti-Semitism to come from the very fringes of society right into the heart of the Labour Party.”
Shadow Chancellor Anneliese Dodds was reportedly due to be touring the studios on behalf of the party this morning, but apparently pulled late last night.
Mr Corbyn’s former director of strategic communications James Schneider claimed that, according to party rules, he had been readmitted to the parliamentary party automatically already.
This sends an appalling message. “Zero tolerance" either means zero tolerance or it's meaningless. The scathing report from the EHRC less than three weeks ago outlined a stream of racism and discrimination by the Labour Party on Jeremy Corbyn’s watch. Yet here we are.
— Karen Pollock (@KarenPollock100) November 17, 2020
He added: “It's automatic. Jeremy Corbyn is a Labour MP with the whip restored. It would be a decision for the leadership to now withdraw the whip if that's what they want to do.”
He went on to defend his former boss, adding: “It’s a clear cut case for reinstatement because nothing that he said or wrote on the day of the EHRC report in any way was anti-Semitic or broke any party rules.”
He added: “The right decision was found because Jeremy Corbyn didn’t say anything that is either factually or morally wrong.”
The decision to readmit Mr Corbyn was made by the party's ruling National Executive Committee [NEC].
The move has sparked a fierce backlash from Labour MPs and Jewish societies. It has been reported that former minister and Jewish MP Dame Margaret Hodge could quit the party.
The Labour veteran said she could not "comprehend" why it was acceptable for Mr Corbyn to "be a Labour MP if he thinks anti-Semitism is exaggerated and a political attack".
She tweeted: "This is a broken outcome from a broken system. A factional, opaque and dysfunctional complaints process could never reach a fair conclusion. This is exactly why the EHRC instructed Labour to setup an independent process!"
Dame Louise Ellman, the Jewish former Labour MP who quit the party over its handling of anti-Semitism last year, said Sir Keir should "refuse to restore the whip" to Mr Corbyn.
Mr Corbyn was suspended after he claimed that the scale of anti-Semitism in the party was "dramatically overstated for political reasons" by opponents and "much of the media". He has since sought to clarify his comments.
Mr Corbyn said he was “pleased” to have been reinstated in the Labour Party. Ahead of a meeting of the NEC disputes committee on Tuesday he acknowledged that concerns around anti-Semitism in Labour were not "exaggerated".
He revealed he had given a statement to the party in an attempt to "clear up any confusion" over his initial response and a broadcast interview given in the wake of the report.
Sir Keir tweeted last night: "Jeremy Corbyn's statement in response to the EHRC report was wrong and completely distracted from a report that identified unlawful conduct in our tackling of racism within the Labour Party. This should shame us all.
"I will not allow a focus on one individual to prevent us from doing the vital work of tackling anti-Semitism. When I stood as leader of the Labour Party, I was clear that my first priority would be to root out antisemitism. It still is.”
Watch: Jeremy Corbyn to have Labour suspension lifted over antisemitism investigation response