Jeremy Corbyn is facing calls from his own shadow cabinet to condemn "intimidation and abuse" of MPs by the Stop the War Coalition as he prepares to attend a fundraising dinner for the group.
Shadow culture secretary Michael Dugher said the Labour leader should use the controversial event this evening to "have a word" with the organisers.
The comments will increase the pressure on Mr Corbyn to distance himself from the movement, which he chaired before taking charge of the party in September.
A number of MPs, including former frontbenchers Tristram Hunt and Caroline Flint, have urged the leader to shun the dinner in the wake of a series of controversial statements about terrorism and air strikes on Syria. Green MP Caroline Lucas has also resigned as a patron of Stop the War, citing concerns about the positions it has adopted.
A tweet and article published in the wake of the attacks on Paris suggested France had "reaped the whirlwind" of Western support for extremist violence in the Middle East.
Both were later removed and disowned by the organisation's leaders, but critics have highlighted a another article last week which argued jihadists were driven by a "spirit of internationalism and solidarity" akin to the International Brigades that fought in the Spanish Civil War.
Again the article was later removed and disowned.
In an interview with The House magazine, Mr Dugher said many Stop the War activists thought "the wrong people won the Cold War" and the dinner was a chance to deliver a message.
"I think it might be quite useful if he (Mr Corbyn) went along to it because he can have a word with them as their former chairman and say to them 'stop the intimidation, stop the abuse and stop the talk of deselections' and going after Labour MPs who voted in a way they didn't approve of," he said.
"Him having a quiet word with some of those guys would be really helpful. What you've got to remember about a lot of these people in Stop the War is that they think the wrong people won the Cold War. To say I might have a slightly different world view is an understatement."
Mr Dugher also lashed out at the Momentum group linked to allies of Mr Corbyn, saying the "aggression" of some activists was "matched only by their stupidity".
"I don't know what the point of them is," he said. "It's the job of Jeremy and all of us in position in the Labour Party to make sure that the Labour Party gets back in touch.
"That's a shared responsibility and a shared burden and you don't need to create a new faction in the Labour Party which has been susceptible to entryists and which has at times resembled the mob."
The Information Commissioner has said he is looking into a complaint about the body, thought to centre on its use of data gathered during the leadership election campaign.
Mr Dugher called for Labour's ruling NEC to consider removing former London Mayor Ken Livingstone, a strong supporter of Mr Corbyn, as co-chair of the party's defence policy review.
"Every time he opens his mouth he manages to offend large numbers of people, so maybe he should just open his mouth a little less," Mr Dugher said. "Ian Murray, the Shadow Scottish Secretary, received an email from someone who lost their fiance in the 7/7 attacks and she switches on the telly and sees Ken Livingstone likening the 7/7 terrorists to martyrs for a cause and blaming western foreign policy.
"What do you think she thinks of the Labour party now? Do you think we can ever get that vote back?
"These were sick maniacs who need to be taken on and beaten for what they are."
Mr Dugher made clear he still backed renewal of Trident, which is implacably opposed by Mr Corbyn. And he warned the leader against ejecting shadow ministers who had defied him by voting for air strikes on Syria.
"We should make a virtue of our differences and be able to have debates. This is the new politics," he said. "I'm not sure how revenge reshuffles sits with the new politics."
Mr Dugher also played down the significance of the Oldham by-election result, where Labour increased its proportion of the vote, albeit on a lower turnout than the general election.
"Oldham was a great result because even when you have a colossally safe seat like Oldham is, and even when you've got an incredibly strong local candidate, you're always nervous going into by-elections," he said. "We got a great result, but one swallow does not a summer make.
"We've got a lot of work to do ahead of what will be a really big test for us, which is the May elections. At this stage we should not just be holding onto places, we should be gaining seats as well. So May's a big test for us all."