Published: 3:43 PM August 27, 2019 Updated: 6:28 PM September 17, 2020

John McDonnell (centre left) and Ian Blackford, sign a declaration saying they will continue to meet as an alternative House of Commons if Boris Johnson temporarily shuts down parliament to get a no-deal Brexit through, watched by Caroline Lucas (left), Jo Swinson and Liz Saville Roberts (right). Photograph: Stefan Rousseau/PA Wire. - Credit: PA

A cross-party group of around 160 Remainer MPs has signed a declaration calling prorogation of parliament to force through a no-deal Brexit an 'outrage', and committing to do 'whatever is necessary' to stop it.

Following a meeting to agree tactics on preventing a no-deal, MPs signed what they are calling the Church House Declaration.

The venue, Church House, served as a meeting place for the House of Commons during the Second World War after it proved resilient to bombing during the Blitz. Speaking at the event, shadow chancellor John McDonnell said Boris Johnson was threatening democracy by considering the prorogation of parliament to push through a no-deal Brexit.

READ: Boris Johnson seeks advice on shutting down parliament for five weeks ahead of Brexit deadlineMcDonnell added: "Prime ministers come and prime ministers go. But actually I don't think we have ever seen a prime minister like this who has the potential to threaten the very nature of our democracy."

Earlier, Remainer MPs met and agreed not to pursue a vote of no confidence in the prime minister but to take a legislative route to blocking a no-deal Brexit.

MORE: Caretaker PM plan on back burner as opposition parties agree tactics to stop no-deal BrexitSenior opposition politicians including McDonnell, Liberal Democrat leader Jo Swinson, SNP Westminster leader Ian Blackford, Plaid Cymru Commons leader Liz Saville Roberts, Green Party MP Caroline Lucas and Change UK leader Anna Soubry were present at the ceremony to sign the declaration.

Former Conservative ministers Guto Bebb, Dominic Grieve, Sam Gyimah and Phillip Lee are also among those who signed.

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The text of the Church House Declaration reads: "Shutting down parliament would be an undemocratic outrage at such a crucial moment for our country, and a historic constitutional crisis.

"Any attempt to prevent parliament sitting, to force through a no-deal Brexit, will be met by strong and widespread democratic resistance.

"We pledge to work together across parties and across our nations to do whatever is necessary to ensure that the people's voice is able to be heard."

Independent MP Luciana Berger, who convened the meeting with Labour MP Stephen Doughty, told PA News Agency she would back MPs meeting at an alternative location - such as Church House - if parliament was prorogued in order to push through a no-deal Brexit.

She said: "There are lots of things that MPs collectively can do together and we will have to make that decision if and when that moment definitively presents itself.

"The challenge at the moment is the hint of prorogation. The prime minister has failed to rule it out."

She added: "I wouldn't purport to be an expert on [parliamentary rule book] Erskine May, but the fact that we come together in this place, where MPs have in the past come together, and it has been officially recognised, is indicative of the fact that it could take place again in the future.

"Ours is a people's parliament. We live in a parliamentary democracy and I hope that parliamentary democracy will be respected and will continue into the decades and centuries ahead.

"We have come together because we face the hint of - the prospect of - a prime minister who might use tools like prorogation to subvert our parliamentary democracy and we will not allow that to happen."

Meanwhile, Jeremy Corbyn has written to 116 Tory and independent MPs, including Theresa May and Philip Hammond, asking them to support efforts to block a no-deal Brexit.

The Labour leader said: "We know there is a majority in parliament against no-deal. As MPs, we've voted against no-deal on a number of occasions and we did so in the largest number on March 27 of this year.

"As you were one of 116 Conservative or independent MPs who voted against no-deal that day and are not on the government frontbench, I am writing to you to offer to work together, in a collegiate, cross-party spirit, to find a practical way to prevent no-deal."