Jeremy Corbyn has signalled that he will strengthen Labour’s stance on a second Brexit referendum before Theresa May is replaced by a new Tory prime minister.

In a move aimed at reassuring party activists rattled by recent local and European elections, the Labour leader stressed that Leave and Remain voters should be offered “real choices” on any ballot paper.

And he said he would announce the new position soon after next week.

During a crunch meeting of the shadow cabinet, several key Corbyn allies threw their weight behind a public vote as the best way to stop Boris Johnson from plunging the country into the chaos of a hard Brexit.

HuffPost UK has learned that John McDonnell, Richard Burgon and Barry Gardiner all called for a stronger stance on a referendum.

Corbyn himself revealed that he had recently been reading Harold Wilson’s biography of how the former Labour PM healed the party with a Europe referendum in 1975.

During the ‘unity referendum’, Wilson allowed different wings of the party to express different views, with left-winger Tony Benn on one side and the PM and his other ministers on the other.

A senior source said that McDonnell told the meeting: “We look indecisive, we look like we’ve been triangulating, we need to make our position clear.”

At a Labour business event, he went further, declaring: “We intend to campaign for ‘Remain’.”

Deputy leader Tom Watson warned during the meeting that “we can change our position at conference but it may be too late by then”. Emily Thornberry said: “We should be true to our internationalist values and campaign for Remain and reform.”

Shadow Brexit secretary Keir Starmer last week called for a new policy of ‘referendum and Remain’, a plea since echoed by Watson.

Corbyn’s fresh focus on the detail of a referendum was seized on by MPs backing a ‘People’s Vote’ as proof that the party was shifting its stance to reverse the haemorrhaging of support to the Liberal Democrats and Greens.

And campaigners were encouraged when Corbyn told the shadow cabinet that he would step up the urgency on the issue by consulting trade unionists next week before making his final view public.

The timing means that Labour’s position will be clarified before a new prime minister succeeds May next month, and prepares it for any fresh Brexit votes in the House of Commons.

With recent general election opinion polls putting Labour in third place behind the Brexit Party and the Lib Dems, activists and close allies have been urging Corbyn not to leave the issue festering until the annual conference in September.

Corbyn’s latest words on Brexit came at a specially convened meeting of the shadow cabinet in the Commons.

He said that he had “stuck faithfully” to his party’s policy agreed at last year’s conference and warned that a no-deal Brexit would “plunge us into the worst excesses of disaster capitalism”.

Corbyn repeated his pledge after the Euro elections that “it is now right to demand that any deal is put to a public vote”.

But he added: “A ballot paper would need to contain real choices for both Leave and Remain voters. This will of course depend on parliament. I will be hearing trade union views next week, and then I want to set out our views to the public.”

His methodical process echoes that seen earlier this year when he consulted MPs and then unions before announcing his support for customs union with the EU.

Party chairman Ian Lavery is still highly sceptical of the shift, but several colleagues who had shared his view have now accepted a change is needed, multiple sources said.

Burgon, a close ally of Corbyn, argued that Johnson’s no-deal threats mean that Labour must now support a public vote on any deal, with the threat to the NHS of a Trump-style UK-US trade deal a key factor.

Corbyn has spent this week meeting Labour MPs in small groups to gauge his next steps.

In a fresh sign of the divisions within the party, 26 Labour MPs in Leave areas wrote to their leader to warn him that a second referendum would “alienate” many of its natural supporters.

A leaked internal document also suggested that a shift towards a referendum would “leave us vulnerable in seats we need to hold or win” in the North and Midlands.

But pollster Peter Kellner warned the analysis was flawed and would “condemn Labour to its fourth consecutive general election defeat” by failing to win back lost Remain voters.

Backers of a public vote were divided over the progress made on Wednesday. One Remain MP who took part in a meeting with Corbyn said they were “pleasantly surprised” at his new tone in private.

However, the leftwing group Another Europe Is Possible group said it was in “disbelief” thatthe shadow cabinet had failed to move the party’s Brexit position more quickly or explicitly.

In one of the more surreal incidents in Labour’s Brexit saga, party chairman Lavery claimed his Twitter account had been interfered with, after he suggested to a journalist that the “real position” of referendum backers was to revoke Article 50.

Shadow ministers were presented with an internal report – passed in full to HuffPost UK – that suggested there was no reason for the party to panic after the recent Peterborough by-election saw the party beat the Brexit Party.

The report stated it was “not obvious, from the evidence of local elections and Peterborough, that a more ‘pro-Remain’ position from Labour would in itself win back voters currently lost to the Liberal Democrats,

“Or in a numerical enough way that would offset leave voters in many of the key marginals, that have lost both recently and over the last few general elections.”

One party source said that the bulk of the report had been written by an official who backed Brexit, while its summary was written by a key member of the leader’s office.

Pollster Kellner said it was not clear that Labour’s victory in Peterborough can be attributed to the party’s ambiguous stance on Brexit.

“The party’s vote-share dropped by 17 points, from 48 to 31%, with the Lib Dems and Greens gathering significant extra support. In any other by-election in recent decades, 31% would mean defeat,” he said.

“Labour owed its victory to the more equal division of the pro-Brexit vote between the Conservative and Brexit parties. Labour was lucky that the large-scale defection of Remain voters did not cost it the seat.”