Labour’s deputy leader, Tom Watson, has said his party is at risk of being taken over by hard-left “Trotsky entryists”, who are “twisting the arms” of young members, sparking a furious response from backers of Jeremy Corbyn.

Corbyn’s campaign team accused Watson of “peddling baseless conspiracy theories,” after the MP for West Bromwich East used an interview with the Guardian to claim that “Trots” are infiltrating Labour.

Watson said many members of the grassroots Momentum movement, set up to support Corbyn’s leadership, are “deeply interested in political change, in building a more equal society, and are just on a journey in politics that they’re new to”. But he suggested some are being manipulated by seasoned hard-left operators.

Facebook Twitter Pinterest Tom Watson asked Jeremy Corbyn to step down for the good of the party. Photograph: Dan Kitwood/Getty Images

“There are some old hands twisting young arms in this process, and I’m under no illusions about what’s going on. They are caucusing and factionalising and putting pressure where they can, and that’s how Trotsky entryists operate. Sooner or later, that always ends up in disaster. It always ends up destroying the institutions that are vulnerable, unless you deal with it.”



He added that some “Trots”, who have returned to Labour after being driven out decades ago, “certainly don’t have the best interests of the Labour party at heart. They see the Labour party as a vehicle for revolutionary socialism, and they’re not remotely interested in winning elections, and that’s a problem.”

In a wide-ranging interview, Watson also condemned Ed Miliband’s decision to hand Labour members the power to choose the party’s leader, calling for the reinstatement of the electoral college, which gave trades unions and MPs a greater role. The deputy leader, who has his own mandate from the party, also called for a return to the system under which Labour MPs elected members of the shadow cabinet.

His intervention came as Owen Smith, who is challenging Corbyn for the leadership, issued a video message of support from Miliband, who described Smith as his “colleague and friend”, and said he could “reach out to every part of the country”, and make the crisis of Britain’s exit from the European Union into a “progressive moment”.

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Watson said he did not blame Corbyn personally for the crisis in the party and instead feels “great sorrow” for him; but a spokesman for Corbyn’s leadership campaign said: “Rather than patronising members and peddling baseless conspiracy theories about ‘Trotsky entryists’, he should be working with Jeremy to unite our party so that we can get back to campaigning to dislodge this Tory government, and help elect a Labour government in its place.”

Watson later hit back, urging John McDonnell, the shadow chancellor and director of Corbyn’s re-election campaign, to distance himself from the strongly-worded statement.

“John McDonnell has consistently made it clear that everyone in our party must be free to express their opinion and be heard respectfully without fear of being shouted down, which is why I simply don’t believe he approved these intemperate words from Jeremy’s campaign.”

The fractious nature of the leadership contest has been underlined by a series of legal challenges to the party’s process in which Corbyn supporters have ended up at war with some on Labour’s national executive committee.

Corbyn’s team claimed that Watson had forced through the decision by the NEC’s procedures committee to appeal against a high court judgment overruling the NEC’s decision to prevent members who joined Labour after 12 January from voting.

Despite the ferocity of the debate, Corbyn’s team, who are confident of victory, hope the party’s annual conference next month will be an opportunity for healing in the party, promising a unity agenda which will “circle the wagons” and convince some party heavyweights to return to the shadow cabinet.

However, allies admit that plans for policymaking at conference are less than complete, given the chaos of the Labour leadership election. The party’s policy forum, scheduled to meet in July, has still not met.

Ambitions for conference could be further derailed both by the high court decision, which could delay the result, and by issues with conference security.

A senior Labour source said it was possible the leadership result would not happen in time for conference if 130,000 new members had to be checked and enough ballots printed and sent out. “We may need to push back the time frame until after conference, if you think about the actual practicalities of getting that ballot out,” the source said.

“Just organising a mailout that big to make sure people have enough time to vote is a big job.”

Around 50,000 new members are understood to have paid £25 to sign up as registered supporters in order to cast their vote in the leadership election. That money will have to be refunded if the high court decision is upheld, potentially costing the party £1.25m.

The decision about extending any deadline for the leadership election will be made by the party’s procedural committee after the result of the appeal is known. It is understood that it is unlikely there will be further appeals by the party.

An even more pressing concern is the current lack of any security provider for the party conference in Liverpool. Last year, Labour’s national executive committee voted to boycott security provider G4S, which had provided security at the conference for two decades, but now one of the largest trade unions has voiced grave concern over the alternative provider Showsec.

Five security firms are reported to have been approached to bid for the 2016 contract. Three declined to bid, with Securitas withdrawing its bid “after completion of a risk assessment”, leaving Liverpool-based company Showsec as the sole eligible bidder.

Showsec are currently involved in a dispute with the GMB over their recognition of trade unions, which says the firm is “not unionised, will not agree to unionisation and indeed have set up the staff association to prevent it”.

In a leaked memo published last week on the Guido Fawkes website, the party’s general secretary, Iain McNicol, was warned that the Home Office may stop the conference taking place if adequate security is not in place, either by reversing the NEC decision on G4S or agreeing to allow Showsec’s provision despite concerns from the unions.

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The party is in “a very difficult position of having to appoint a potentially anti-union organisation to a high-profile role at annual conference”, the memo said, adding that party HQ “are under pressure from the Home Office to make an appointment very soon ... it must be noted that should we be unable to appoint a security contractor, it is within the power of the Home Office/police to stop conference taking place.”

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The situation is no closer to resolution, with one senior Labour party source saying the security row had more chance of derailing the conference than the leadership election.

“We are a soft target for terrorism and the Home Office could cancel it if we don’t have security,” the source said. “It needs to be resolved as soon as possible. Announcing the leadership result at conference or delaying it might be academic if we can’t sort out a supplier.

“Everyone was concerned about the long-term consequences [of the NEC decision about G4S] at the time, but we still haven’t been able to resolve it. If you ban McDonald’s, you can’t go ahead with this company.”

Though Corbyn’s team see conference as an opportunity to build bridges, Momentum will hold its own fringe conference to coincide with the official Labour event in Liverpool. The event, expected to be attended by Corbyn and McDonnell, will be free and open to those who are not Labour party members.