THERESA MAY'S Brexit strategy has been dealt a devastating blow after the House of Commons rejected her EU Withdrawal Agreement by an overwhelming majority for the second time.

MPs voted by 391 to 242 against the deal, despite the Prime Minister's assurance that new agreements reached with Jean-Claude Juncker in Strasbourg would ensure the UK cannot be trapped in the controversial backstop arrangement indefinitely.

Although the 149 margin was reduced from the record 230-vote defeat of the first "meaningful vote" in January, Mrs May was left far adrift from a majority with just 17 days to go to the scheduled date of Brexit on March 29.

European Commission president Mr Juncker had already warned that if MPs turned down the package agreed in Strasbourg on Monday, there would be "no third chance" to renegotiate.

In line with a promise set out by Mrs May last month, MPs are now due to vote on Wednesday on whether they are willing for the UK to leave the EU without a deal on March 29.

If they reject no-deal as most Westminster observers expect, a third vote will follow - probably on Thursday - on authorising Mrs May to request an extension of the two-year Article 50 negotiation process.

An extension requires the unanimous agreement of all 27 remaining member states, and Mr Juncker has warned that it cannot stretch beyond May 23 unless the UK takes part in the European Parliament elections starting on that date.

Cabinet gave its approval to Mrs May's package at an early-morning meeting in 10 Downing Street which ended with the PM telling colleagues: "Today is the day. Let's get this done."

But the momentum moved sharply against the Prime Minister shortly afterwards, as Attorney General Geoffrey Cox released formal legal advice that the changes secured by Mrs May "reduce the risk" that the backstop will be permanent, but do not remove it altogether.

The Prime Minister made a statement after the result of the vote was read out, saying that the choices facing the UK were "unenviable", but because of the rejection of her deal, "they are choices that must be faced".

Mrs May said she "profoundly regrets the decision this House has taken tonight".

"I continue to believe that by far the best outcome is the UK leaves the European Union in orderly fashion with a deal," she said.

"And that the deal we have negotiated is the best and indeed only deal available."

Announcing a free vote, Mrs May told MPs: "This is an issue of grave importance for the future of our country.

"Just like the referendum there are strongly held and equally legitimate views on both sides.

"For that reason, I can confirm that this will be a free vote on this side of the House."

The Prime Minister said she had "personally struggled with this choice" but the best way to leave was "in an orderly way" with a deal.

Mrs May stressed her responsibilities for Northern Ireland, where Stormont is still suspended.

She said: "I'm conscious of my duties as Prime Minister of Great Britain and Northern Ireland and the potential damage to the union that leaving without a deal could do, when one part of our country is without a devolved government."