Speaker rules out third vote on May's deal if unchanged
John Bercow's decision is a major blow to the Prime Minister who wants to table her deal again.
The Speaker of the House of Commons has ruled out a third so-called "meaningful vote" on Theresa May's Brexit deal if the motion is "substantially the same".
John Bercow told MPs that the Prime Minister "cannot... resubmit to the House the same proposition, or substantially the same proposition, as that of last week".
The Speaker's ruling is a heavy blow to May, who had reportedly been considering whether or not to table her deal for a third vote this week.
The withdrawal agreement she struck with Brussels in November was decisively rejected for a second time last Tuesday by 149 votes - the fourth largest Commons defeat for a government in history.
It followed January's first meaningful vote on the deal, which saw the government's motion crushed by a record-breaking margin of 230.
Bercow highlighted the Prime Minister's cancellation of a vote on her deal back in December, which came after three days of Commons debate on it, repeating that he found that action "deeply discourteous" to MPs.
Citing parliamentary precedent, he continued: "If the government wishes to bring forward a new proposition that is neither the same nor substantially the same as that disposed of by the House on March 12, this would be entirely in order.
"What the government cannot legitimately do is resubmit to the House the same proposition - or substantially the same proposition - as that of last week, which was rejected by 149 votes.
"This ruling should not be regarded as my last word on the subject.
"It is simply meant to indicate the test which the government must meet in order for me to rule that a third meaningful vote can legitimately be held in this parliamentary session."
The Speaker said the convention dated back to 1604 and told MPs it had been confirmed again many times, including in 1864, 1870, 1882, 1891 and 1912.
He added: "One of the reasons the rule has lasted so long is that it is a necessary rule to ensure the sensible use of the House's time and the proper respect for the decisions it takes."
Bercow said last week's second meaningful vote had been acceptable because there were a number of legal changes to the deal, as well as the publication of three new documents.
There was no immediate response from Downing Street to Bercow's statement.
The Prime Minister's official spokesman said: "The Speaker did not warn us of the contents of the statement or indeed the fact that he was making one."
It comes as May prepares to go to Brussels on Thursday for the European Council, where she is expected to ask for a delay to Brexit by an extension of Article 50.
She has previously said that unless her deal was passed by Parliament by then, she would need to request a long extension, delaying Brexit for months, or even years.