Former prime minister Tony Blair has said it can if that’s what people want. We look at the technical possibilities, and probabilities

Tony Blair has said Brexit could still be stopped. Is he right?

Theoretically, yes. Theresa May is adamant that Brexit will go ahead when she triggers article 50 before the end of March, and has insisted there will be no second referendum. At the moment it is verging on political heresy to say the UK should not proceed with leaving the EU, because that was the democratic outcome of the referendum. However, there was nothing binding about the vote and no legal obligation for the government to pursue Brexit.

Tony Blair: Brexit could be stopped if Britons change their minds Read more

How would it actually happen?

The most straightforward technical way of stopping Brexit is to not trigger article 50, which fires the starting gun on two years of negotiations with the EU. After this point, there are conflicting legal views on whether it would be possible to rescind notification that Britain wants to leave. Some, such as Donald Tusk, the EU council president, believe the UK could withdraw its application to leave, but others, including the British government, hold that it would be a one-way track to the exit door.

Would any politician actually want to stop Brexit in the next four months?

At the moment, the majority of MPs are in favour of respecting the result. There are a few exceptions, including some Liberal Democrats and the former Labour leadership contender Owen Smith, who want another referendum after a deal with the EU has been negotiated; and a handful of diehard remainers, such as the Europhile Tory MP Ken Clarke, who want to halt the process altogether. This could probably only change if there was an obvious shift in the public mood towards staying in. That could push politicians to rethink their fervour for carrying out the “will of the people” in favour of Brexit. However, such a shift is unlikely before the end of March.

Is there anything procedural that could stop article 50 being triggered?

There is a high court ruling that says parliament must give its approval for Brexit before article 50 can be triggered. The government is appealing against this, but if the judgment stands MPs could theoretically prevent Brexit. It is unlikely, however, that they will do so given that Labour has indicated it will support legislation paving the way for Britain’s exit – likely to be in the form of a three-line parliamentary bill. On the other hand, MPs may try to hold up the process by asking for more details about May’s strategy and demands before giving their approval. While there is a majority of MPs in favour of proceeding with Brexit, there is probably no majority for a hard Brexit involving a clean break with the single market and customs union.

What conditions could move the public mood far enough to halt Brexit after that?

Economic gloom popularly blamed on Brexit could conceivably cause voters to rethink their support for leaving the EU. In his interview with the New Statesman, Blair suggests this is one of two situations in which people could change their mind about Brexit. He says people might reconsider if the exit terms negotiated with the EU looked so economically damaging that the “pain-gain” ratio made it no longer worthwhile. But there is a strong argument that this would only happen if and when people’s jobs, finances and lives had already started to be affected by an economic slump.

The second situation outlined by Blair is that the exit terms negotiated with the EU seem so similar to the status quo that people question whether the UK should bother leaving. This is perhaps a less likely scenario because May has been adamant that she will not accept one of the fundamental pillars of the EU: freedom of movement. At the moment, there appears to be little appetite from EU leaders to change their rules to keep the UK in the bloc, although international politics can shift substantially during two years of negotiations.

Would there need to be another referendum to prove voters had changed their minds?

Probably, or a general election won by a party campaigning to drop Brexit. The crunch point would come at the point of May returning from Brussels with an exit deal, and if parliament felt the result was not satisfactory and decided to vote it down. It would be difficult for the prime minister to avoid giving the Commons and Lords a vote at this point.

If this happened, the prime minister could either try to negotiate a better deal, or decide to bypass parliament by getting her own mandate for the deal. Her choices would be to hold a general election, or run another referendum, either on the terms of the deal, or on whether to proceed with leaving at all, bearing in mind that it is not yet clear that article 50 can be withdrawn once triggered.

The decision to call another referendum would be highly contentious and divisive. Leave campaigners would not give up without a fight, especially if there were to be a narrow result in favour of staying in.

Could Scotland, Wales or Northern Ireland put an end to Brexit?

The government does not accept that the devolved administrations have a veto, although it has promised to give them a consultative role in the process of leaving the EU. However, the Scottish and Welsh governments have been allowed to take part in the supreme court appeal, which may determine how much say they have over the Brexit process through their own legislatures.

Scotland is the most likely to want to halt Brexit as its voters wanted to stay in the EU. Further down the line, Scottish National party MPs in Westminster could play a role in trying to block any deal done by May, clubbing together with MPs from other parties if they do not like the terms.

In Northern Ireland, the ruling Democratic Unionist party is in favour of Brexit but a campaigner for victims of paramilitary violence has won the right to a hearing in the supreme court aimed at blocking Northern Ireland from leaving the EU.