The Labour Party faced fresh calls to sack one of Jeremy Corbyn’s key aides after he was found to have launched an online tirade against Israel, accusing it of “genocide”.

Joss MacDonald, a party speechwriter, also branded Israel an “apartheid state”, and claimed its conduct is permitted only “because of the Holocaust”, according to a Daily Mail report.

The row erupted only days after Labour confirmed that Ken Livingstone, the Mayor of London between 2000 and 2008, would have his suspension extended for claiming that Adolf Hitler “was a Zionist”.

In the aftermath of the 2014 Gaza conflict, Mr MacDonald tweeted: “Sounds like an admission that Israel is committing genocide and that you’re excusing it because of the Holocaust.”

Four years earlier he accused Israel of “killing the two state solution”.

On Saturday evening Conservative MP Andrew Percy called for Mr MacDonald to be sacked, branding his anti-Israel tweets “disgusting slurs”.

Mr Percy, who is Jewish, said: “Jeremy Corbyn should reconsider his decision to employ this man.’ Jeremy Corbyn promised a ‘kinder politics’ but he continues to turn a blind eye to people around him who do and say things which are unacceptable in public life.

“These tweets show yet again that Labour have a systematic problem with anti-Semitic racism which needs to be addressed urgently.”

The affair has reignited a debate within the party over whether criticism of the state of Israel – and the policies of its government – constitutes antisemitism.