The UK has been offered a delay until May 22 on the proviso MPs agree the third iteration of Theresa May’s withdrawal deal, which she is expected to try to bring back to the Commons next week.

However, speaker of the house John Bercow – citing a ruling dating to 1604 – says he will block a third vote unless the prime minister can demonstrate substantial change to the bill.

MPs voted down May’s initial withdrawal agreement in January by a record 230 votes. A second vote following renegotiation with the EU was defeated by 149 votes.

If MPs do not back May’s deal, the EU will permit a shorter delay until April 12 to allow the UK to agree a deal or “indicate a way forward”.

May initially pursued a June 30 extension. However, this was rejected by the EU on the grounds it would clash with European Parliamentary elections.

The prime minister has said MPs now have a choice between leaving in an “orderly manner” or face the prospect of the country fielding candidates for the elections three years after the vote to leave.

She has also ruled out revoking Article 50, the legal mechanism allowing the UK to leave the European Union, after a petition urging her to do so achieved more than one million signatures in less than 24 hours.

The petition has now been signed by more than 2.5 million people.