Britain's opposition Labour party was facing fresh turbulence on Sunday over an ongoing anti-Semitism row which has seen a donor pull out and a comedian appointed to its governing body.

Property tycoon David Garrard, who has donated around £1.5 million ($2.1 million, 1.7 million euros) to Labour since 2003, hit out at the way party has been run by leader Jeremy Corbyn.

"I have watched with dismay and foreboding the manner in which the leadership has, in my view, over the last two years, conducted itself," he told the Observer newspaper.

"I consider that it has supported and endorsed the most blatant acts of antisemitism," Garrard added.

Corbyn has been under increasing pressure to address multiple allegations of anti-Semitism within the party, which last week saw Jewish campaigners hold a protest outside parliament.

Just days later the official in charge of Labour's disputes panel, Christine Shawcroft, resigned over allegations she opposed the suspension of a candidate accused of Holocaust denial.

On Saturday Shawcroft stepped down from the party's national executive committee.

She was replaced by comedian Eddie Izzard, who called on Labour to "stamp out completely the stain of anti-Semitism from a minority of members".

"We must make amends and repair the damage with the Jewish community as Jeremy Corbyn has promised to do," he said.

Meanwhile an investigation by The Sunday Times into 20 of the biggest pro-Corbyn Facebook groups found more than 2,000 anti-Semitic, racist, misogynistic, violent and abusive messages.

A Labour spokesman said none of the groups were run by or officially connected to the party, while British media reported Sunday that Corbyn's personal Facebook account had been deleted.

His professional page remains and on Friday was used to post a Passover message by the veteran politician.

"It's easy to denounce anti-Semitism when you see it in other countries, in other political movements. It's sometimes harder to see it when it's closer to home," Corbyn said in the video.

"We all need to do better. I am committed to ensuring the Labour party is a welcoming and secure place for Jewish people," he added.

On Thursday Corbyn told Jewish News that there had been 300 internal party referrals for anti-Semitism since 2015, around half of which led to expulsions or resignations.