LONDON (Reuters) - British Prime Minister Theresa May is facing likely defeat in parliament on Tuesday when she asks lawmakers to approve her Brexit deal - a decision that would trigger huge uncertainty about the future of Britain’s exit from the European Union.

Britain's Prime Minister Theresa May leaves from the back of 10 Downing Street in London, Britain, January 14, 2019. REUTERS/Clodagh Kilcoyne

May has warned that rejecting her deal opens up the possibility of Brexit being stopped, or that Britain leaves disruptively without a deal. She has promised to respond quickly to any defeat.

So what could happen next if she loses?

BACK TO PARLIAMENT

May must submit a new plan for Britain’s next steps by the end of Jan. 21. It is not clear what May’s ‘Plan B’ is, but some local media have reported she would ask parliament to vote again on the deal, perhaps after seeking another set of reassurances from the EU.

Some lawmakers have floated the idea that parliament could, in a temporary break from convention in Britain, take control of the process away from the government and hand it to a committee of senior lawmakers from across the political spectrum.

It is not clear that this plan is technically possible, or whether it has enough support to succeed. The government said any attempt to prevent it from meeting its legal obligation to deliver an orderly EU exit would be extremely concerning.

RESIGN

May could resign as leader of the Conservative Party, triggering an internal contest to replace her without a general election.

OUSTED

May defeated an attempt to oust her as leader of the Conservative Party in December, winning a confidence vote by 200 votes to 117. The result means her position as leader of the party cannot be challenged for 12 months.

VOTE OF NO CONFIDENCE

The opposition Labour Party has said it will call a vote of no confidence in the government if May’s deal is rejected, but has not specified exactly when.

If a majority of lawmakers vote against May’s government, Labour would have 14 days to prove, by a vote, that it could command a majority and form its own government. That would allow Labour to take control of the country without an election..

BACK TO THE BALLOT

If May’s government loses a confidence vote and Labour is unable to form a new government, an election is called. May could also call a general election herself if two-thirds of lawmakers in parliament agree to it. May has said that a general election is not in the national interest.

LONGER-TERM OPTIONS:

SECOND REFERENDUM

The route to a second referendum on Brexit - or a People’s Vote - is unclear.

But, unless the plan to give control of the process to parliament is successful, it would require the backing of the government of the day. A new referendum can be called only if it is approved by parliament.

With May dead-set against a second referendum, and the opposition Labour Party not committed to one (but not ruling one out), a second referendum would need either a change in prime minister, a change in government, or an abrupt change in policy.

An increasingly vocal contingent of lawmakers from across the political spectrum supports a fresh vote to break the impasse in parliament. But, so far they have not been able to prove there is a majority in parliament for this view.

Even if parliament did agree in principle to a second referendum, Britain would then have to ask for an extension to its timetable for leaving the EU.

DELAY OR CANCEL BREXIT

The government could seek to extend the negotiating period with the EU to give it time to try to reach a better deal, hold a general election, or conduct a second referendum.

The government could also withdraw its notice of intention to leave the EU, which the European Court of Justice has ruled it can do without consent of other EU countries.

May has said she does not want to delay Britain’s exit from the EU, and will not revoke the notice of intention to leave.