As the row deepened, 75 MPs and 14 MEPs wrote to Labour’s governing body to demand that “a clear commitment” to another referendum be included in the party’s manifesto for next month’s European parliament elections.
Mr Corbyn’s top team is split on whether Labour should support a second referendum. Several senior shadow cabinet ministers want the party to support a public vote on any Brexit deal passed by parliament, but Mr Corbyn’s inner circle say he only supports a referendum on the government’s deal or to avoid a no-deal outcome. Other shadow ministers oppose another public poll entirely.
In their letter to the National Executive Committee (NEC), the MPs and MEPs said Labour had “a clear opportunity to win these elections” if it fully supports a Final Say vote.
They wrote: “These elections are about the kind of Europe we want to live in, and we can’t make a convincing case in them without being clear about Brexit. Labour has already, rightly, backed a confirmatory public vote. The overwhelming majority of our members and voters support this, and it is the democratically established policy of the party.
“Our members need to feel supported on doorsteps by a clear manifesto that marks us out as the only viable alternative to Nigel Farage’s Brexit Party.
“We need a message of hope and solidarity, and we need to campaign for it without caveats. To motivate our supporters, and to do the right thing by our members and our policy, a clear commitment to a confirmatory public vote on any Brexit deal must be part of our European election manifesto. We understand the many different pressures and views within our movement, but without this clear commitment, we fear that our electoral coalition could fall apart.”
The MPs and MEPs said “the world is watching” and that Labour “must be ready to rise to the challenge”. They added: “We must run a dynamic, energetic campaign around a radical manifesto to transform Europe and a clear position on Brexit.”
The letter was organised by the Love Socialism, Hate Brexit group. Signatories included 10 current shadow ministers, House of Commons Brexit select committee chair Hilary Benn and former shadow cabinet ministers including Angela Eagle, Debbie Abrahams, Rachel Reeves and Owen Smith.
Several prominent supporters of Mr Corbyn, including shadow Treasury minister Clive Lewis and former international development secretary Kate Osamor, have also added their names.
It came as Labour MPs, MEPs and party members reacted with fury to the leaked draft campaign leaflet, which suggested Labour would deliver Brexit by seeking “a better deal with Europe”.
The flyer made no mention of another referendum, saying only: “The Tories’ chaotic handling of Brexit has left our country in crisis.
“With Labour, Britain will have a proper say in future trade deals and businesses wouldn’t have to pay to trade with Europe.
“Labour will keep a close relationship with the EU and protect workers’ rights.”
It is understood that the leaflet, which was drawn up by Mr Corbyn’s team and staff at Labour’s HQ, was not signed off by shadow cabinet ministers or Labour MEPs.
Sir Keir Starmer, the shadow Brexit secretary, was said to be “furious” at the omission of the party’s policy on another referendum.
Sources said many MPs were also infuriated by the draft.
One Labour MP told The Independent: “People went into complete meltdown and were utterly furious at what appears to be yet another attempt by a small cabal of disgruntled officials to undermine the entire rest of the party, with no reference to the very candidates these leaflets are meant to promote.”
They added: “It’s quite extraordinary to see this early draft of a leaflet which makes no mention of Labour’s key conference policy on Brexit, especially just a day after the international commission [of Labour’s National Policy Forum] responsible for drawing up our policy on these issues unanimously supported a confirmatory vote.
“I sincerely hope this is an early draft because it would be unacceptable for unelected officials to attempt to subvert Labour’s members, trade unions and elected representatives in this way.”
Mr Corbyn has struggled to keep his divided shadow cabinet together on the issue of on another referendum. Some of his closest advisers and shadow ministers, including party chairman Ian Lavery, shadow Cabinet Office minister Jon Trickett and shadow business secretary Rebecca Long-Bailey are staunchly opposed to another vote. But others, led by Sir Keir and deputy leader Tom Watson, have pushed hard for the party to support a Final Say vote.
A Labour spokesperson said: “There are a number of different texts for different leaflets in circulation, including for a freepost and for other campaign purposes. They all reflect existing party policy. Our manifesto for the European elections will be decided next Tuesday.”