Momentum, the Labour-supporting group that grew out of Jeremy Corbyn's leadership campaign, is split down the middle following a meeting of its core activists on Saturday that resulted in accusations of bullying, a divided group of supporters, and the claim from one of its own national committee members that there is a secret plot to transform the organisation into a rival left-wing political party to Labour.
Although ostensibly an argument over what form of internal voting structure to use, the dispute at the national committee meeting highlighted the increasingly bitter divisions between activists who want to turn the group into a mass online activist movement in the style of Bernie Sanders' US presidential campaign and those who want to organise along traditional left-wing lines.
Originally formed to defend Corbyn's position as Labour leader, Momentum faces a struggle between multiple firmly entrenched factions that want to control the group.
Laura Murray, the newly elected Momentum women's representative, accused fellow activists of attempting to turn the group into a rival political party that would ultimately stand candidates against Labour, writing on her blog: "Jeremy Corbyn will inevitably make one compromise or concession that isn’t ideologically-pure enough for them and they will abandon him and Labour altogether to turn Momentum into a rival left-wing party."
She added: "Naively, I assumed that all Momentum members would be focussed on building a positive and unprecedented movement to transform the Labour Party and society.
"I never could have imagined the sheer capacity that some people have to endlessly argue with each other, either over the boring bureaucracy of structures and process or pointless motions on policies they can’t implement because they’re not actually a party."
Murray accused Marxist Alliance for Workers Liberty (AWL) supporter Jill Mountford of "shouting at the younger delegates, heckling them when they spoke, patronising and mocking them directly to their faces, and leaping up out of her chair to contradict every statement they made", and said the veteran left-wing campaigner had reduced Labour Students BAME officer Huda Elmi to tears.
Mountford, who has been expelled from the Labour party over her association with AWL, told BuzzFeed News the depiction of her on the blog was wrong. She said it was "complete fiction" that she wanted to turn Momentum into a separate political party, describing the group as "the best opportunity the radical left have had for 35 years".
She also strongly denied accusations of bullying and said the vigorous debate over internal structures at Saturday's meeting was simply democracy in action: "You pay your money and take your chance when you join a political organisation.
"If you go to a meeting and you’re not winning and you start calling for recounts, then expect that people might get upset and heckle. Don’t try and gerrymander a vote to get your own way, then you won’t get shouted out ... No one shouted more in that conference than Huda."
Jon Lansman, a long-time ally of Tony Benn and Jeremy Corbyn who co-founded the group, is facing criticism over his decision to retain personal control of all its valuable membership data. He wanted to hand control of key decisions to Momentum's 20,000 members using online balloting, but his opponents successfully maintained the existing system, which is based on sending delegates from local branch meetings.
Earlier this year Momentum was discussing hiring extra staff and expanding its remit into pro-Labour campaigns but the group now faces a simmering battle over its internal structure.
Michael Chessum, an activist who attempted to propose a compromise solution to bring both sides together, insists a formal split with Momentum is unlikely but warned in a blog post that a "kind of paralysis" could affect the organisation if the warring sides cannot come to a compromise.
Meanwhile, Momentum LGBT* representative Josie Runswick said debate at the meeting "was often heated, heckling was common and disruptive and the conduct of those on both sides of the arguments was often poor".
A spokesperson for Momentum insisted the group was pushing ahead with its campaign work, saying: "Momentum's National Committee met on Saturday to discuss a full agenda, including motions, campaigns and plans for our first national conference – featuring robust debate and close votes. National Committee members will meet again in January ahead of February's inaugural conference, which will determine how Momentum moves forward to build our grassroots, campaigning movement that will help secure a Labour government."
However, even those who support this view admit the organisation is at a crossroads.
"I don't doubt Momentum will get through this period," said one key individual involved in the group. "The dynamism in the organisation and opportunity for a new political movement is too great to be held back. But Saturday's fractious meeting means it's going to be a fucking hard slog."