Voting down the Prime Minister's Brexit deal for a third time would cause a "political meltdown", a minister has warned, after Theresa May admitted she may not garner enough support to get her plan through the Commons next week.
Nadhim Zahawi said Parliament would have "failed" if the twice-defeated Withdrawal Agreement is rejected by MPs again, as he said he was "not prepared" to tell his constituents the UK would not leave the European Union.
The Education Minister's comments came as tens of thousands of people descended on central London demanding a second referendum on Brexit in the "Put it to the People" march.
Meanwhile, pro-Brexit campaigners continuing their long hike from the North East to the capital were joined by former Ukip leader Nigel Farage near Nottingham.
Mr Zahawi told BBC Radio 4's Today programme: "If Parliament decides to vote down the Prime Minister's Withdrawal Agreement then I think it would be political meltdown and Parliament would have failed."
He added: "Each and every one of us will have to ask ourselves the question: 'Am I prepared to go back to my constituents and say we're not leaving the EU, we're going to go for a much longer extension, and we're going to take part in the European elections?'
"I'm not prepared to do that. I don't think the Prime Minister is prepared to do that."
Elsewhere, former Conservative chancellor George Osborne called for a long delay to the Brexit process.
"The best outcome now would be a long delay, and it's not the worst thing in the world to ask people to vote for some MEPs, and certainly better than stockpiling medicine and turning Kent into a car park," he told Today.
"So I think the best outcome is a long delay where we rethink how we deliver on the referendum result and we try and find a majority for a compromise Brexit agreement and possibly have a second referendum."
And ex-prime minister Tony Blair, who advocates a second referendum, called for a proposed series of "indicative votes" on alternatives to Mrs May's Brexit deal to be delayed, saying it would be better to have a debate in a less frenzied atmosphere.
Mrs May wrote to MPs on Friday night warning that if there is insufficient support for her Withdrawal Agreement in the coming days that she could seek an extension to Britain's EU membership beyond the European Parliament elections.
The PM said the UK could revoke Article 50; leave without a deal; ask for an extension beyond April 12 if her deal is rejected or not voted on; or leave on May 22 if it is finally approved.
Mrs May wrote: "If it appears that there is not sufficient support to bring the deal back next week, or the House rejects it again, we can ask for another extension before 12 April - but that will involve holding European Parliament elections.
"If it appears that there is sufficient support and the Speaker permits it, we can bring the deal back next week and if it is approved we can leave on 22 May."
Amid mounting speculation about the Prime Minister's future in Number 10, Prisons Minister Rory Stewart said replacing her would not help the situation.
"I would rather she stayed because I don't believe that changing Theresa May for someone else is going to resolve this problem," he told BBC Two's Newsnight.
"The problems are deep in the wounds of the vote, Parliament, the European Union - it's not about a single individual."