Boris Johnson faces commons showdown over no-deal Brexit
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.
By David Hughes, PA Political Editor
Boris Johnson will face a parliamentary battle when MPs return to Westminster next week after opposition leaders agreed to work together to stop a no-deal Brexit.
The Prime Minister has repeatedly promised the UK will leave the European Union on October 31, with or without a deal, and allies accused the opposition group of trying to "sabotage" the UK's position in talks with Brussels.
After cross-party talks led by Labour's Jeremy Corbyn, a co-ordinated effort to thwart Mr Johnson's plans has been promised based on passing new legislation when the Commons returns from its summer break on September 3.
The leaders agreed to prioritise a legislative approach rather than an effort to oust Mr Johnson.
Mr Corbyn confirmed he would not immediately push ahead with a move to replace Mr Johnson through a vote of no confidence.
That idea had met resistance because of his plan to lead a caretaker government. Other opposition figures had called for a compromise candidate who would be more likely to command a cross-party Commons majority as an interim prime minister.
Mr Corbyn said: "We are putting first the legislative proposal next week and that's what the agreement was reached this morning to do, that's what we are doing.”
"The motion of no confidence will be put, by me, at an appropriate time but obviously not the first item next Tuesday, because I believe it's important that we get on with a legislative process which prevents the Prime Minister acting in defiance of the will of Parliament - which was demonstrated by an enormous majority saying that we do not believe this country should crash out without a deal.”
"The Prime Minister needs to respect Parliament and understand the role of Parliament is to question and challenge the executive."
The Labour leader has also written to 116 backbench Tory and independent MPs who have previously voted against a no-deal Brexit, urging them to work with him.
Recipients include ex-prime minister Theresa May and her chancellor Philip Hammond, along with other former Cabinet ministers who oppose a no-deal outcome.
Mr Corbyn said: "They will get the letter just like everyone else and I hope that they will reflect that they voted against no deal - as indeed I did, as indeed many, many other colleagues did from all parties - because crashing out without a deal I think would be very bad for our economy and be quite disastrous for many industries and jobs in this country."
SNP Westminster leader Ian Blackford said Mr Johnson had "no mandate or majority" and the numbers were stacking up against him.
"Parliament must grasp this opportunity, unite to stop Boris Johnson shutting down democracy - and be ready to use all mechanisms to block a no-deal disaster, including deploying legislation as a priority," he said.
Liberal Democrat leader Jo Swinson said: "I am pleased the meeting focused on a legislative route which we have agreed is the best way forward and are now looking at all the scenarios to deliver this."
Independent Group for Change leader Anna Soubry said: "We agree we will work together to stop a no-deal Brexit by legislation."
Plaid Cymru leader Adam Price said: "We committed to work co-operatively with every other opposition party and do everything in our power to avoid a catastrophic crash-out Brexit."
Over the coming days contact will be maintained at lower levels, with representatives "wargaming" strategies to create a legal barrier to a no-deal Brexit.
Mr Corbyn said he would put forward a proposal for the process, but the legislation would be a cross-party effort with support from some Conservative MPs.
Mr Johnson tweeted that "the referendum result must be respected" and restated his commitment to the October 31 date.
A Number 10 source said: "We are now making progress because our European partners realise we are serious about leaving the EU on October 31 - no ifs, no buts.”
"It's utterly perverse that Corbyn and his allies are actively seeking to sabotage the UK's position.”
"This coalition of anti-democrats should be honest with the British public, they are against us leaving the EU no matter what.”
"The Government believes politicians don't get to choose which public votes they respect."