Britain will hold elections to the European Parliament later this month regardless of what happens in ongoing talks with the opposition to pass a Brexit deal, Prime Minister Theresa May's de facto deputy said on Tuesday.

"Given how little time there is... it is regrettably not going to be possible to finish that process before the date that is legally due for European parliamentary elections," David Lidington said in televised comments.

After twice delaying the date of Brexit, the government had hoped it could get a draft divorce deal through parliament before the deadline so it would not have to go ahead with the elections on May 23.

"We very much hoped that we would be able to get our exit sorted and have the treaty concluded so that those elections did not have to take place," Lidington said.

Lidington added that the government would be "redoubling our efforts and talks with MPs of all parties to try to make sure that the delay after that is as short as possible.

"Ideally we'd like to be in a situation where those MEPs never actually have to take their seat at the European Parliament, certainly to get this done and dusted by the summer recess," he said.

The newly-elected European Parliament is due to meet for the first time on July 2. The British parliament's summer recess is due to start on July 20.

"That will mean effort, hard work and compromise from different political parties, people from both the Leave side and the Remain side in the European debate," Lidington said.

The decision to hold the EP elections means that Britons resident in Malta will also have a right to vote in the elections held here, and vice-versa.