Brexit: Why might the UK have to take part in European elections this May?

With the repeated rejection of Theresa May’s Brexit deal, the prime minister has said she aims to ask for a further extension to the Brexit process to allow the UK to leave the European Union "in a timely and orderly way".

The prime minister offered to hold talks with Labour leader Jeremy Corbyn to agree a plan acceptable to both, which can be put to the House of Commons ahead of the 10 April summit of the European Council.

Speaking in 10 Downing Street after a marathon session of Cabinet lasting over seven hours, Ms May said that any further delay to Brexit should be "as short as possible".

She said a bill to pave the way for departure would have to be in place by 22 May to ensure the UK did not have to take part in European Parliament elections.

The elections are scheduled to take place from Thursday 23 May until Sunday 26 May across the EU.

Different countries hold their votes on slightly different days, as suits them.

The EU treaties are very clear: every EU member state has to hold European parliament elections, because the union’s citizens have an inalienable right to be represented at an EU level. If the UK hasn’t left by the end of May, it would still be an EU member state, and have to take part.

The legal text of the Lisbon Treaty says that “in each member state, members of the European parliament shall be elected as representatives of the citizens of the union”. It’s pretty unambiguous.

There isn’t any legal basis on which a member state could decide not to take part in elections – there’s no specific opt-out for countries undergoing Article 50.

The general view is that there is no legal way for Britain to avoid the elections. The UK’s own Electoral Commission has set aside a contingency fund in case it needs to hold the elections, and it says it has “assumed that, should the elections go ahead in the UK, polling day would be Thursday 23 May”.

Other member states including Belgium and Finland have also asked British nationals living in their territory to register – just in case they have to take place.

Jean-Claude Juncker, the European Commission president, agrees. He said himself in a letter on Tuesday: “I would like to stress that the United Kingdom’s withdrawal should be complete before the European elections that will take place between 23-26 March this year. If the United Kingdom has not left the European Union by then, it will be legally required to hold these elections, in line with the rights and obligations of all member states as set out in the treaties.”

The EU is based on rules, and those rules are governed by an independent court – the European Court of Justice. It would be extremely unlikely to turn a blind eye, especially if confronted with a legal challenge.

Given the weight of legal evidence that Britain must take part – and our divided political system – there would almost certainly be a legal challenge. Even if nobody from the UK mounted a challenge, other groups across the EU could use the argument to challenge the results of the European elections.

Given the European Commission is selected based on the results of the European elections, the consequences could be significant – undermining the mandate for the Commission to pass laws.

The UK’s seats in the European parliament have already been split up amongst the other member states, so it really needs to know whether Britain is taking part before the seats are allocated.

If the UK left part-way through a parliamentary term there would also be the question of what to do with missing seats. Does the parliament just have a hole in it for just under five years until the next round of votes? Do the countries hold by-elections? Because different answers to these questions benefit different people, they will be difficult and divisive to solve.

Aside from the practical reasons, there are also political reasons why the UK isn’t really wanted in these elections. The focus of this round of elections is expected to be stemming the tide of populism in Europe. Some polls suggest populist parties could win a third of seats.

As one of the biggest member states, the UK returns a lot of MEPs – and it mostly returns them to the populist groups. Ukip won the 2014 elections in the UK and provides the bulk of members to the anti-EU EFFD group, while even the Conservatives sit in the hard-right ECR group, away from the European mainstream.

Donald Trump’s former adviser Steve Bannon has said he wants to unite populist forces across the EU, and British MEPs – who are also more Atlantacist than their continental cousins – could give him the numbers to make a go of it.

Some parties, such as the Liberal Democrats and SNP, have already selected candidates lists, based on the possibility that there might be elections. Former Ukip leader Nigel Farage has also set up a new Brexit party to stand in the elections and keep his platform in the European parliament – from where he attacks the EU and British government. Other parties – including Labour and the Tories – haven’t picked candidates – yet.

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