The Speaker of the House of Commons has ruled that U.K. Prime Minister Theresa May cannot bring her Withdrawal Agreement to a third vote in Parliament, following two decisive defeats, a move that effectively means she must now ask European Union officials for a long extension to the March 29 Brexit deadline.

Citing Parliamentary precedent from the 17th century, Speak John Bercow said May's deal, which was first unveiled in mid November, agreed by European officials on November 25 and subsequently rejected on January 15 by 230 votes, the largest defeat in U.K. history, cannot be brought back to the House in its same form.

Bercow said last week's vote, which May lost by 149 votes, contained three new documents, including statements from the EU, that made it materially different from the January vote. However, Bercow said "it has been strongly rumored that a third, and even a fourth, meaningful vote motion may be tabled by the government. 

"If the government wishes to bring forward a new proposition, that is neither the same nor substantially the same as the one disposed of by the House last week", he would allow it. However, "what the government cannot legitimately do is resume to the House the same proposition, or substantially the same proposition that was brought to the House on March 14."

The pound slipped sharply lower against the U.S. dollar following the Speaker's decision, falling 0.7% from its session high to around 1.3206.

U.K. lawmakers voted overwhelming in favor last week of a government motion to ask the European Union for an extension to the March 29 deadline for Britain to leave the European Union in order to allow for more time to establish a majority for Britain's post-Brexit future.

The vote gave May one final chance, before March 20, to bring her twice-defeated Brexit deal to Parliament, after which she planned to ask for a "technical extension" to the deadline until June 30.

With May's spokesperson saying earlier today that no new negotiations with the European Union scheduled, and the EU itself insisting it won't push the current deal any further forward, May is now effectively unable to bring a third attempt the Parliament and will likely now seek a longer extension from EU officials.

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