Talks come as the number who have signed petition on parliament website to stop Brexit passes 4.6 million

Pro-Remain MPs are drawing up plans for a vote on revoking article 50 as an emergency measure to stop Britain crashing out of the EU, after an online petition to cancel Brexit became the most popular ever.

By Saturday night more than 4.6 million people had signed the petition on the parliament website, which states: “A People’s Vote may not happen – so vote now”.

Public discussion about halting Brexit was considered politically toxic until just days ago. But that shifted last week as the prospect of crashing out drew closer and the number of petition signatures rose dramatically.

A cross-party group of parliamentarians is now examining the possibility of cancelling the Brexit process, following concerns that Theresa May could end up backing Tory MPs who favour a no-deal departure if her own withdrawal agreement is rejected again. They are planning to table an amendment to Brexit legislation closer to the day of Britain’s scheduled departure from the EU.

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The European court of justice ruled late last year that Britain could unilaterally revoke article 50, although not just to buy time. Writing on theguardian.com, the Tory MP Phillip Lee said that the people had to be given an opportunity to reconsider Brexit and that one way of allowing this to happen would be to revoke article 50. “Mrs May should ensure that the UK has the time and the space to do this in a properly considered way – either by seeking a long extension of article 50, or by taking back control and revoking it altogether.”

The petition to revoke is now both the most popular since parliament set up the online site, and has also been signed at the fastest rate. Parliament is now obliged to consider it for debate, but MPs see the timing of announcing any bid to revoke article 50 as crucial.

The petition was boosted by celebrities including Hugh Grant, Jennifer Saunders and Brian Cox. The woman who created it said on Saturday that she had faced a huge volume of online abuse, three death threats by phone, and would be closing her Facebook account after it was hacked.

Margaret Georgiadou, 77, was “shaking like a leaf” after the phone threats, she told the BBC. She also said she had no memory of old posts she allegedly made on social media, using threatening language about the prime minister. “It must have been a cut and paste job,” she said. “The dates were all wrong.”