A cross-party group of around 160 MPs has signed a declaration to support doing “whatever is necessary” to stop a no-deal Brexit.
Meeting at Church House in Westminster – a meeting place for the House of Commons during the Second World War – the MPs signed what they are calling the Church House Declaration.
Speaking at the event, shadow chancellor John McDonnell said Prime Minister Boris Johnson was threatening democracy by not ruling out proroguing Parliament to push through a no-deal Brexit.
Senior opposition politicians including Mr 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.
Former Conservative ministers Guto Bebb, Dominic Grieve, Sam Gyimah and Phillip Lee are among those to sign the document.
Ms Berger told the 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.”
She continued: “I will certainly do everything I can within my means to hold the Prime Minister to account and to ensure he doesn’t pursue that reckless and very dangerous path.”
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.”
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.”