LONDON - The government has made a fresh plea to MPs to get behind Theresa May’s Brexit deal in Tuesday’s crucial Commons vote.

A group of MPs are understood to be planning to take control of the Brexit process if, as widely expected, Mrs May’s deal is voted down. And Labour leader Jeremy Corbyn has vowed to table a vote of no confidence in the government if she loses, which could trigger a general election.

The PM has warned of a “catastrophic” breach of trust if Brexit is thwarted.

Writing in the Sunday Express, Mrs May told MPs: “It is time to forget the games and do what is right for our country.”

Tuesday - Day five of debate followed by “meaningful vote” on the PM’s deal. MPs will also get to vote on amendments that could reshape the deal

If the deal is rejected Theresa May will get three working days to come up with a “plan B”

Wednesday - Mrs May is likely to head to Brussels to try get further concessions from the EU Monday, 22 January - Commons vote on “Plan B” - MPs are reported to be planning to amend this vote to wrest control of Brexit from the government

Friday, March 29 - the UK leaves the EU, unless MPs have succeeded in delaying or cancelling it Brexit Secretary Stephen Barclay told the BBC’s Andrew Marr show: “There are lots of different plans being put forward by Members of Parliament that don’t respect the result (of the referendum) or risk no deal.”

Pressed on what happens if the deal is defeated, Mr Barclay said he suspected the Commons would support something “along the lines of this deal” but declined to speculate on whether the government had a Brexit “plan B”.

He told the Andrew Marr show: “We will table a motion of no confidence in the government at a time of our choosing, but it’s going to be soon, don’t worry about it.”

The Labour leader has said his party does not have the votes in Parliament to win a confidence vote on its own and has appealed to other parties to support it.

Northern Ireland’s DUP party, which keeps Mrs May in power, is also planning to vote against her deal but has said it will support Mrs May in a confidence vote.

If a majority of MPs back a no confidence motion, the government - or anyone else who can command a majority - will get 14 days to try to win another confidence vote. If no-one can’t do that, a general election will be held.

Mr Corbyn is facing growing calls from within his own party to back a second EU referendum. He told Andrew Marr he hoped to get a general election first - and ensure that the UK did not leave without a deal.

“My own view is that I’d rather get a negotiated deal now, if we can, to stop the danger of a no-deal exit from the EU on 29 March - which would be catastrophic for industry.”

A “no-deal” Brexit is where the UK would cut ties with the European Union overnight without a transition period.

Theresa May’s government, and many others, believe this would be hugely damaging and want a more gradual withdrawal. But if Parliament can’t agree on that, and nothing else takes its place, the UK will leave without a deal. This would mean the UK would not have to obey EU rules. Instead, it would need to follow World Trade Organization terms on trade. Many businesses would see new taxes on imports, exports and services, which are likely to increase their operating costs. That means the prices of some goods in UK shops could go up.

The UK would also lose the trade agreements it had with other countries as a member of the EU, all of which would need to be renegotiated alongside the new agreement with the EU itself.

The UK would be free to set its own immigration controls. However some UK professionals working in the EU and UK expats could face uncertainty until their status was clarified. The European Commission has said that even in a no-deal scenario, UK travellers won’t need a visa for short visits of up to 90 days.

The border between Northern Ireland and the Irish republic would become an external frontier for the EU with customs and immigration controls, though how and where any checks would be made is not clear.

Some Leave supporters think that leaving without a deal would be positive if the right preparations were made. They say criticism is scaremongering and any short term pain would be for long term gain.

But critics - including both Brexit supporters and opponents - say that leaving without a deal would be a disaster for the UK: driving up food prices, leading to shortages of goods and gridlock on some roads in the South East resulting from extra border checks.

He said he would have to ask the EU to extend Article 50, the legal process taking the UK out of the EU on 29 March, if he won an election, which he said would take place in February or March, to allow time for a new Labour government to negotiate a Brexit deal of its own. Mr Corbyn wants the UK to be part of a customs union with the EU, with access to the single market.

The UK will leave the EU on 29 March unless there is a new act of Parliament preventing that. Because the government controls the timetable for Commons business, it was assumed that this would not be possible.

But a group of MPs, including former Tory ministers, are reported by the Sunday Times to be working on a way to allow non-government members to take control of the timetable and bring forward legislation making it illegal to leave the EU without a deal, if Mrs May loses Tuesday’s vote.

Downing Street has said it is “extremely concerned” about the reported plot, which it says could potentially overturn centuries of Parliamentary precedent.

Currently, the government has precedence in the House of Commons. It controls how and when business, including legislation, is organised. However, some backbenchers are seeking to wrest that control away from them.

If MPs can get an amendment to change how and when Commons business is arranged passed by a majority, backbench business could then take precedence over government business. This could represent a threat not just to Brexit legislation but to the government’s ability to govern, says Downing Street.

It would mean that without control over time in the Commons, the government has no control over parliamentary business, so cannot get through policies and legislation easily.

In terms of Brexit, it means MPs could block a no-deal by making it a legally binding requirement for government to stop Brexit on 29 March.

The SNP’s leader at Westminster, Ian Blackford, said MPs must now take control of the Brexit process from the government to prevent a no-deal scenario.

He told the BBC’s Sunday Politics programme: “The prime minister’s got to stop threatening Parliament and indeed, threatening the whole of the United Kingdom, that it’s a choice between her deal and no deal - that’s not the case.”

Lib Dem leader Sir Vince Cable, who like Mr Blackford backs another EU referendum, said: “I think Parliament will take control of this process, will insist that we pursue the option of no Brexit.”

Sir Vince said this could happen by cancelling Article 50 - which he noted would be “resented by lots of people” - or via a second referendum.

But former Brexit Secretary David Davis said MPs should vote down Mrs May’s deal - and the government should then go back to the EU with “our best and final offer” of a free trade deal with no tariffs, along the lines of the deal the EU has with Canada.

“If the EU insists on no deal, then fine,” he says in an article for the Sunday Times.

The government has previously rejected Mr Davis’s proposals, which are backed by other Brexiteer Tories, saying they would not solve the Northern Irish border problem.