A member of Labour's National Policy Forum has been suspended from the party over an alleged anti-Semitic post.
George McManus said deputy leader Tom Watson had received "£50,000+ from Jewish donors," adding: "At least Judas only got 30 pieces of silver".
Labour has launched an investigation after Labour MP Luciana Berger submitted a formal complaint about his "anti-Semitic" comments.
Mr McManus has apologised to Mr Watson and deleted the Facebook post.
He told BBC News: "It was a stupid, crass error that was insensitive, wrong, inappropriate and hurtful."
Mr Watson has faced calls to quit as deputy leader from supporters of Jeremy Corbyn after he criticised the Labour leadership's handling of an anti-Semitism row.
Thanks to those who drew attention to the appalling, antisemitic comment made by George McManus earlier today. We understand that he has now rightly been suspended from Labour. We will not tolerate any antisemitism, racism or online abuse from candidates we support.— Momentum (@PeoplesMomentum) August 6, 2018
Some critics have accused him of taking money from the "Israel lobby".
Mr McManus made reference to donations Mr Watson has received from businessman Sir Trevor Chinn, who is vice-president of the Jewish Leadership Council.
Mr McManus, followed up his post by suggesting that Mr Watson had been "bought" or "compromised".
Ms Berger flagged up the post to Labour Party HQ, telling them: "Please see attached social media post. It's anti-Semitic and I'd like it to be investigated."
In a statement on Facebook, after deleting the posts, Mr McManus said: "I'd like to apologise to Tom Watson for my drawing an analogy between him accepting money from Jewish donors and the biblical story of the betrayal by Judas.
"I fully accept that such an analogy is wrong and am sorry for making the comparison."
Momentum said Mr McManus's comments "were a classic anti-Semitic trope, and had nothing to do with Israel".
The campaign group said he had "rightly" been suspended by the party, adding: "We will not tolerate any anti-Semitism, racism or online abuse from candidates we support."
Mr Corbyn has repeatedly vowed to take firmer action against anti-Semitism and attempted to assure the Jewish community that he is taking the issue seriously.
"We have been too slow in processing disciplinary cases of, mostly online, anti-Semitic abuse by party members. We're acting to speed this process up," he said in a video at the weekend.
But his refusal to endorse in full the International Holocaust Remembrance Alliance's examples of what constitutes anti-Semitism has led to accusations from Jewish community leaders and some Labour MPs that he is not doing enough.
Sir Trevor has donated funds to several other Labour MPs in recent years, including Owen Smith, who in 2016 made a failed bid to oust Mr Corbyn as leader.