British Prime Minister Theresa May. Brexit by July 1 unless UK votes in EU election: Document Ambassadors told of legal issues raised by delay to Britain’s departure.

Brexit can't be delayed beyond July 1 unless Britain takes part in the European Parliament election at the end of May, according to an EU document presented to ambassadors of member countries on Friday.

The document, prepared by EU officials, sets out the legal issues that would be raised by Britain requesting an extension of the Article 50 period, as Prime Minister Theresa May is expected to do next week.

The text states that a withdrawing member country is legally bound to organize European Parliament elections between May 23 and May 26 this year. If the member country does not do so and the new Parliament holds its first session on July 2 with that country still in the bloc, the EU institutions "cease being able to operate in a secure legal context."

"It follows that no extension should be granted beyond 1 July unless the European Parliament elections are held at the mandatory date," the document says.

The document says that multiple extensions to the Article 50 period are theoretically possible. But if the U.K. were granted an extension until July 1 and did not take part in the European Parliament election, it could not then be given a further extension.

"It follows that if an initial extension puts the withdrawal date after the date of the European Parliament elections, and if these elections were not organised by the withdrawing State, this would make any further extension impossible," the document says.