Labour’s civil war entered a bitter new phase with Jeremy Corbyn and his deputy Tom Watson locked in a public spat about whether the party risks being taken over by hard left activists driven out in the 1980s.

Watson sent the leader’s office a four-page document, based on publicly available information, detailing what he said was evidence that Trotskyists had been attending meetings of grassroots pro-Corbyn Momentum pressure group and seeking to influence the Labour leadership election.

He claimed some of the individuals involved were members of other parties, including the Socialist party, the successor to Militant, whose members were expelled from the Labour party by Neil Kinnock.



The evidence included reports from the Socialist party’s website of its members addressing Momentum rallies and tweets from an activist expelled from Labour earlier this year who appeared to be running phone banks backing Corbyn in the leadership race.

Watson’s letter was a riposte to the accusation made on Tuesday by Corbyn’s campaign that he was “peddling conspiracy theories” after he said in a Guardian interview that Labour was at risk from “Trotskyist entryists”.

Watson wrote: “It’s not a conspiracy theory to say that members of these organisations are joining Labour. It’s a fact.”

Labour deputy leader Tom Watson's letter to Jeremy Corbyn Read more

The Socialist party’s leader, Peter Taaffe, a founder member of Militant who has continued to be involved since the 1980s, told the Guardian earlier in the day that he hoped to be readmitted to the Labour party if Corbyn saw off the leadership challenge from Owen Smith.

He said Corbyn was opening Labour up “to all strands of socialist and working class opinion” and rejecting control of the party by a “top-down, centralised elite”. He added: “The lava of this revolution is still hot.”

The Socialist party published an editorial on Tuesday which argued for a Labour split, even if it meant the party was left with just 20 MPs. “The civil war, now it is out in the open, cannot be simply called off,” the editorial said.

Taaffe said: “[Watson] is referring to entryists, but we were not entryists, we were born in the Labour party, and we were expelled because we fought Thatcher in Liverpool and defeated her.” He insisted that Labour MPs critical of Corbyn could not “stop the winds of history as they’re developing at the moment”.

Smith’s campaign received a fillip on Wednesday when he was endorsed by the GMB union after he won a ballot of its members, 60% to 40%. Its general secretary, Tim Roache, said: “GMB members cannot afford for Labour to be talking to itself in a bubble for the next five years while the Tories run riot through our rights at work, our public services and our communities.”

Corbyn’s allies blame the result on “GMB political officers close to Watson” and claimed the ballot question “Who do you think is best placed to lead the Labour party to a general election victory and serve as prime minister?” was a leading one, because it made reference to electability.

Former shadow chancellor Chris Leslie ridiculed that claim: “If you don’t think you can be considered as a potential future prime minister, then what sort of leadership are you talking about? This boils it right down to whether we just want to be some sort of protest movement.”

Smith and Corbyn will face each other in their second live hustings in Gateshead on Thursday night, but Labour is still involved in a legal wrangle over the rules of the contest, with the national executive committee’s appeal against a high court judgment forcing it to give the vote to 130,000 recent members due to be heard.

Some Labour activists regarded the victory of six pro-Corbyn candidates in the NEC elections announced earlier this week as a signal that he would win re-election by a wide margin.

Meanwhile Saving Labour, the group that has been encouraging sceptics of Corbyn to get involved in the leadership contest, say they have convinced 50,000 trade union members, targeted through social media and in addition to 70,000 people who paid the £25, to sign up as registered supporters in order to vote.

“This contest is far from over. Our success in this campaign shows that a huge number of trade union members want to see new leadership, and will vote accordingly when ballot papers drop in a couple of weeks.

Members of rival political parties that stand candidates against Labour are not allowed to join, but some MPs complain that veterans of its bitter internecine struggles in the 1980s, some of them allied to banned groups, are involved in the current battles.

In his letter to Corbyn, Watson said: “I assume that you still support the proscription of other political parties. If the position had changed, please just let me know because I think it would be useful to discuss this within the party.

“I am asking you to confirm that you believe members of the Socialist party and the Alliance for Workers’ Liberty should not be allowed to be members of the Labour party, given the proscription of these two groups [then called Militant and Socialist Organiser] by annual conference during Neil Kinnock’s leadership.”

A spokesman for Corbyn responded to Watson’s claims: “It’s absolute fantasy and, if this is the way they want to characterise new Labour party members, then it’s not going to do them any favours in the leadership contest.”

He added that the party’s policy on refusing to allow members of other parties to join Labour had not changed.

However, sources close to Corbyn said there would be nothing to stop Socialist party members renouncing their membership and joining Labour, comparing the situation to defections from the Greens or Conservatives. They also argued that the party’s compliance unit, which vets applications for membership, is, if anything, too quick to exclude leftwingers on political grounds.

Watson said he had been “reliably informed” that some members of Momentum were consciously adopting the tactics used by Militant in the 1980s, including tips for infiltrating local constituency Labour parties published in Michael Crick’s history of the movement.

The advice, which Watson reproduced in full in his letter to Corbyn, includes suggestions such as: “Make the event adversarial. Uncomradely questions to sitting councillors and the MP, challenging the chair’s method and motive, defining the politics of the speaker before they have defined their own. This behaviour basically reduces the attendance of the remaining sensible types. Then the meeting [is] ours to control.”

A Momentum spokesperson insisted they did not recognise the quotes, saying: “The description quoted from Michael Crick’s book runs entirely contrary to Momentum’s ethos and ways of organising. Momentum members and supporters would have no truck with the type of described in this alleged quotation.”

Relations between the Labour leader and his deputy have broken down dramatically since Watson joined calls for Corbyn to resign in the wake of a no-confidence vote from more than three-quarters of Labour MPs.

Kinnock’s victory over Militant in the 1980s is regarded as a key moment by both wings of the Labour party. Corbyn’s win in last year’s leadership election, and the resulting decisive shift towards the left, has raised hopes among some of those excluded then of being readmitted.

Watson stressed that he believedmany members of the rapidly expanding Labour party and the pro-Corbyn pressure group Momentum are “genuine in their desire to campaign vigorously against Tory inequality”. But he added: “There is no denying that tightly organised factions are also organising within Momentum and the party.”

His evidence included reports from the Socialist party’s website of its members addressing Momentum rallies and calls for them to attend Keep Corbyn events.

He claimed that Jill Mountford, who was banned from Labour earlier this year for being a member of the Alliance for Workers’ Liberty, had been organising phone banks in support of Corbyn’s reelection bid, citing tweets she had made.

Facebook Twitter Pinterest Relations between Corbyn and Watson have broken down since no-confidence vote of Labour MPs. Photograph: Dan Kitwood/Getty Images

‘I want to hug him but also shout at him’: Tom Watson on Jeremy Corbyn and Labour rifts Read more

He included a link to a booklet produced by the Socialist Workers party, whose banners are often seen at Momentum rallies, advising members on how to capitalise on Corbyn’s leadership of Labour.