Parliament has already rejected it twice by substantial margins. But with a deadline of March 29 approaching -- at which the UK crashes out of the EU unless an agreement is reached -- May's government hoped to bring the deal back a third time. But Bercow ruled that, according to parliamentary procedure, the government could not repeatedly put a motion before lawmakers if it had been previously rejected in the same session.  Bercow said that, in his view, the first two motions on May's Brexit deal were sufficiently different not to have broken parliamentary convention.

This is the first time in  UK politics that a UK Speaker has invoked the rule dating back to 1604 under which the House of Commons should not be asked to make a decision on the same question twice. Bercow said the UK can propose a vote on a new deal which must be appreciably different from previous proposals.