Theresa May has warned of a “catastrophic and unforgivable breach of trust” in democracy if MPs reject her Brexit deal and the UK remains in the European Union.

With just two days to go before the Commons vote on her withdrawal agreement, the prime minister pleaded with parliamentarians to “do what is right for our country” and back her controversial exit plan.

May said the UK risks crashing out of the EU without a deal or, if MPs are “unwilling” to face the uncertainty of no deal, then the UK may not leave at all.

In what she described as the “biggest and most important decision that any MP of our generation will be asked to make”, the prime minister said it was time for politicians to “deliver” for the people.

Writing in the Sunday Express, May said: “You, the British people, voted to leave. And then, in the 2017 General Election, 80% of you voted for MPs who stood on manifestos to respect that referendum result. You have delivered your instructions. Now it is our turn to deliver for you.

“When you turned out to vote in the referendum, you did so because you wanted your voice to be heard. Some of you put your trust in the political process for the first time in decades. We cannot – and must not – let you down.

“Doing so would be a catastrophic and unforgivable breach of trust in our democracy. So my message to Parliament this weekend is simple: it is time to forget the games and do what is right for our country.”

Her stark warning came as Downing Street said it was “extremely concerned” about a backbench plot to change Commons rules to enable backbench motions to take precedence over Government business if May’s deal falls.

Under the rebels’ plan, reported in the Sunday Times, the Government would lose control of parliamentary business which would threaten Brexit legislation and the Government’s ability to govern. It was previously thought only ministers could put a halt to Britain leaving with no deal.

Elsewhere, it emerged that Speaker John Bercow met Tory remain rebel Dominic Grieve on Tuesday, the day before his controversial decision to allow MPs a vote on Grieve’s amendment to the timetable of the Brexit deal.

As speculation mounted that May’s deal would be defeated:

The prime minister faced calls from a predecessor, Sir John Major, to revoke Article 50 to halt Brexit – as he warned it would be “morally reprehensible” to crash out without a deal.

• Pressure mounted on Jeremy Corbyn to trigger a confidence vote in the Government, but shadow chancellor John McDonnell said his party would make such a move when “the time is right”.
• It emerged that 14 military planners have been deployed to four key Whitehall departments to assist with no-deal planning, according to a Freedom of Information request by the Observer.
• More than 100 MEPs from 26 EU member states signed a letter calling on the UK to “reconsider” the Brexit decision, saying the UK’s departure will “weaken all of us”.

May faced further opposition to her deal from her former Brexit secretary Dominic Raab.

He used an article in the Sunday Telegraph to urge MPs to vote down May’s “bad” deal to send a message to Brussels that the UK “will not be bullied”.

He said if it is defeated, Britain should continue to press the EU for a deal that “respects the referendum but if Brussels’ “intransigence” persists “we must be willing to leave the EU at the end of March on World Trade Organisation terms”.