If no agreement can be found to break the political deadlock at Westminster, the UK is currently scheduled to leave the European Union (EU) on 12 April under a no-deal Brexit.
That’s the date when the two-week extension to the negotiating process between the UK and the EU, known as Article 50, formally runs out.
But what is Article 50 and how could the government get it extended again?
Article 50 is part of the Lisbon Treaty that sets out what happens when a country decides that it wants to leave the EU.
It allows an initial two-year period for negotiations on a divorce – finalising a withdrawal agreement and drawing up the broad outlines of a future relationship.
Theresa May and her fellow EU leaders agreed both of those but their deal has been rejected – in successive votes – in the House of Commons.
The UK was due to leave on 29 March (two years after Article 50 was triggered) but, because no agreement could be reached at Westminster, the prime minister asked the EU for a delay to avoid the UK leaving without a deal.
So if she needs another extension, how would she go about it?
The UK makes a request
The UK cannot make a decision about extending Article 50 on its own – it needs the agreement of all 27 other EU countries.
That’s what happened when the original 29 March deadline was extended.
On that occasion, the request was made in a letter from Theresa May to the European Council, on 20 March.
The EU agreed to delay the UK’s departure although not the UK’s suggested date, of 30 June.
Instead, it offered two alternative dates:
– until 22 May, if MPs voted through the government’s withdrawal agreement (by 29 March).
– until 12 April, if they rejected it – the EU says the UK must say what it wants to do next by this date, or leave without a deal
If a new extension is sought, the UK will need to submit its request to EU27 leaders ahead of an emergency summit on 10 April – just two days before the new Brexit deadline.
Any extension would also need to be approved by votes in the House of Commons and the House of Lords, allowing the government to make a simple change to the law removing the reference to the current exit day (12 April) and replacing it with another date.
The EU’s decision
But the EU is not obliged to say yes to the UK. Other EU leaders will want to know, ahead of the summit, precisely why the UK is asking for a further extension.
And one thing is now clear – the EU has said the UK cannot stay in the EU beyond 23 May if it doesn’t take part in the European elections that begin on that day.
The European Parliament’s legal service had argued that an extension to the end of June would be fine because the new parliament would not have held its first session by then.
But EU leaders have sided with a stricter legal interpretation put forward by the European Commission, which argued that allowing the UK to stay in the EU without taking part in European elections was far too much of a risk.
A longer extension?
The prime minister has been firm in saying that she isn’t asking for a longer extension because she “shares the frustration” that many people feel about the Brexit process and she doesn’t want the country to take part in the forthcoming European elections.
But a longer extension may be the only thing on offer.
If the EU decided to offer the UK a delay of between nine and 12 months, or even longer, there could be a get-out clause: an understanding that the UK could leave the EU earlier than the specified date if the government managed to get an exit deal passed in Parliament.
A long extension could also buy time for either an early UK general election or even another Brexit referendum. For now, the government says it doesn’t want either of those.
Michel Barnier, the EU’s chief negotiator has said a long extension carried “significant risks for the EU” and that a “strong justification would be needed” before the EU would agree.
What next, then? Only Prime Minister Theresa May knows it…