UK Prime Minister Theresa May has written to European Council President Donald Tusk to request Brexit be extended to June 30.

In the letter, the prime minister asks for the option to terminate the extension earlier but accepts that if the UK is still a European Union member state on May 23 it will have a legal obligation to take part in the European elections.

She tells Tusk that the UK will make responsible preparations if her withdrawal agreement is not ratified before the trigger date.

Britain is due to leave the EU at the end of next week, but May is seeking to delay Brexit for a second time after her deal was rejected for a third time last week.

She adds: The Government will want to agree a timetable for ratification that allows the United Kingdom to withdraw from the European Union before 23 May 2019 and therefore cancel the European Parliament elections, but will continue to make responsible preparations to hold the elections should this not prove possible.

EU sources have said Tusk will recommend the UK be offered a one-year Brexit extension, with a break clause should a Brexit deal be agreed by MPs, when leaders meet for a crunch summit on Wednesday.

May wants her preferred date of June 30 to be flexible, however, writing: If the parties are able to ratify before this date, the Government proposes that the period should be terminated early.