Jeremy Corbyn is being urged to intervene to help settle the breach in Momentum, as the troubled organisation’s internal divisions again spilt into the open after a fractious meeting of the organisation’s national committee left Jon Lansman, the organisation’s founder, contemplating exercising his “nuclear option” and shutting down the group completely.

Proposals to give decision-making power to the whole of Momentum’s membership were narrowly defeated, with the organisation resting on a delegate system. The public argument advanced by Lansman’s allies, who backed the one member, one vote system, was that the e-ballot would give greater control to members as opposed to bogging the organisation down in hidebound procedures.

But privately, insiders admitted the plan was a gambit to see off Lansman’s internal critics, including the Alliance of Workers’ Liberty, a Troskyite grouping, who are small but well-organised, giving them an advantage over the rest of the membership.

In a blog, Laura Murray, the newly-elected women’s representative, said publicly what allies of Lansman have been saying privately for some time: that the plan of the AWL and its allies is to take over Momentum with a view to setting it up as a rival party to Labour.

Lansman’s critics, however, say that he is treating Momentum as his personal fiefdom and is stifling the internal democracy of Momentum. The division, which first flared into life following the row over Jackie Walker’s remarks at Labour party conference, has taken on an additional dimension due to the growing frustration of some at what they see as the leadership’s right turn on immigration, free movement and taxation. Clive Lewis’ remark that free movement “has not worked” and John McDonnell’s support for the 40p rate cut are particular causes for alarm.

However, Jeremy Corbyn’s popularity remains largely undimmed, and the Labour leader is coming under pressure to intervene in the row. Lansman has also met with Andrew Murray, who as well as being the father of Laura Murray is Unite general secretary’s Len McCluskey’s chief of staff and a key link into the Labour leader and McCluskey himself. One trade union official said “I think it’s time for Jeremy and John to intervene to straighten out the situation, so we can get on with the job of holding the government to account”.

Should Corbyn refrain from wading in, Lansman still retains the ability to shut down Momentum, taking its valuable maillist with him, and starting again from scratch. However, the so-called “nuclear option” would mean crippling the left in its internal battles with the Corbynsceptics ahead of crucial clashes about conference delegates and parliamentary selections.