John McDonnell has suggested a second referendum now seems "inevitable" if MPs reject Theresa May's Brexit deal.

In a significant intervention, the shadow chancellor also said Labour would call on the government to "join us" in a public vote if Labour cannot secure a general election - the party's preferred option.

Labour's official position is to keep all options on the table, including the prospect of a second referendum, but Jeremy Corbyn has made it clear he disapproves of a new public vote.

Mr McDonnell told the BBC: "We want a deal that will protect jobs and the economy. If we can't achieve that - the government can't achieve that - we should have a general election but that's very difficult to do because of the nature of the legislation that David Cameron brought forward.

"If that's not possible, we'll be calling upon the government then to join us in a public vote.

"It's difficult to judge each stage, but that's the sequence I think that we'll inevitably go through over this period."

Asked if it was "inevitable" that there would be another vote, he said: "That's right. Our policy is if we can't get a general election, then the other option which we've kept on the table is a people's vote."

Labour MP Stephen Doughty said his comments were “very welcome", adding: "It would be good to see this repeated and reinforced as it becomes clearer by the hour that we need a way through this Brexit chaos.

"It's clear that it is the will of Labour members and voters across the country.”

The Independent has launched a campaign for a Final Say referendum on Ms May’s Brexit deal, which has attracted more than a million supporters so far.

In a separate interview, Mr McDonnell also said for the first time that staying in the bloc should be one of the alternatives offered to the public in the event of a public vote.

He came under fire at the party's annual conference when he said Labour would “go for a people's vote” if MPs rejected Theresa May's deal but without the option to halt Brexit altogether.

Pro-EU MPs were dismayed by his comments, with one MP telling The Independent that denying voters the choice to remain in the EU as "farcical".

Mr McDonnell told a Guardian event: "If we can’t get a general election, people’s vote is on the table and that might be an option we seize upon."

The Labour frontbencher said he would vote to remain in a fresh poll and dismissed the idea of presenting the public with the option to crash out of the EU without a deal.

“We can’t have no deal on the ballot paper,” Mr McDonnell said.

Cabinet ministers resign over Brexit deal Show all 13 1 /13 Cabinet ministers resign over Brexit deal Cabinet ministers resign over Brexit deal Esther McVey Britain's Work and Pensions Secretary Esther McVey arrives to attend the weekly meeting of the cabinet at 10 Downing Street in London. - Britain's Work and Pensions Secretary Esther McVey resigned from the cabinet over draft Brexit deal AFP/Getty Cabinet ministers resign over Brexit deal Handout image taken from the Twitter feed of @EstherMcVey1 of the resignation letter addressed to Prime Minister Theresa May from Works and Pensions Secretary Esther McVey. PRESS ASSOCIATION Photo. Issue date: Thursday November 15, 2018. Ms McVey has resigned, saying the Brexit deal âdoes not honour the result of the referendumâ. See PA story POLITICS Brexit. Photo credit should read: @DominicRaab/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. PA Cabinet ministers resign over Brexit deal Dominic Raab British Brexit Secretary Dominic Raab give a press conference at the end of the final round of talks in Brexit negotiations at the European Commission in Brussels, Belgium EPA Cabinet ministers resign over Brexit deal Handout image taken from the Twitter feed of @DominicRaab of the resignation letter addressed to Prime Minister Theresa May from Brexit Secretary Dominic Raab. PRESS ASSOCIATION Photo. Issue date: Thursday November 15, 2018. Mr Raab has resigned, saying he âcannot in good conscience support the terms proposed for our deal with the EUâ. See PA story POLITICS Brexit. Photo credit should read: @DominicRaab/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. PA Cabinet ministers resign over Brexit deal Rehman Chrishti Vice Chairman of the Conservative Party Rehman Chrishti tendered his resignation letter this afternoon PA Cabinet ministers resign over Brexit deal Cabinet ministers resign over Brexit deal Anne-Marie Trevelyan Parliamentary private secretary in the Department of Education Anne-Marie Trevelyan resigned stating that she cannot support the deal Cabinet ministers resign over Brexit deal Handout image taken from the Twitter feed of @annietrev of the resignation letter addressed to Prime Minister Theresa May from Anne-Marie Trevelyan, a parliamentary private secretary in the Department for Education. PRESS ASSOCIATION Photo. Issue date: Thursday November 15, 2018. Ms Trevelyan has resigned saying she cannot support the Brexit deal after negotiations âbuilt on the UK trying to appease the EUâ. See PA story POLITICS Brexit. Photo credit should read: @annietrev/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. PA Cabinet ministers resign over Brexit deal Sam Gyimah Universities minister Sam Gyimah resigned on November 30, claiming the government's decision to pull out of the EU's Galileo satellite navigation system as a deciding factor PA Cabinet ministers resign over Brexit deal Shailesh Vara Shailesh Vara who has quit as Minister of State for Northern Ireland, saying he cannot support Theresa May's Brexit agreement, which he said "leaves the UK in a halfway house with no time limit on when we will finally be a sovereign nation" PA Cabinet ministers resign over Brexit deal Cabinet ministers resign over Brexit deal Suella Braverman Brexit minister Suella Braverman has resigned, stating “It is not what the British people, or my constituents, voted for in 2016.” Cabinet ministers resign over Brexit deal Ranil Jayawardena Parliamentary private secretary to the ministry of justice Ranil Jayawardena resigned as he could not back the deal "in good conscience"

“There’s an overwhelming majority in parliament against that happening, because of the damage.”

He said MPs were likely to vote down the prime minister's deal, forcing Ms May to return with a tweaked blueprint that would be rejected as well.

Mr McDonnell said: “All through that, we will be calling for a general election.

“Whether and when we put a vote of no confidence down will be a tactical decision. We’ll want a maximum effect.”

He said that Labour had been meeting with the SNP, the Lib Dems and Green MP Caroline Lucas to discuss.

It emerged at the weekend that Mr McDonnell had met with former Labour spin doctors Alastair Campbell and Tom Baldwin, who are senior figures from the People’s Vote campaign for a fresh referendum.

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However sources close to Mr McDonnell advised that Labour’s policy had not changed and that he was still pushing for a general election.

Meanwhile, Mr Corbyn’s spokesman told reporters that Labour would oppose the Brexit deal on offer, adding: “If that deal falls our position is that a general election would be the best outcome.