Britain is set on course for a delayed Brexit after MPs inflicted a second humiliating defeat on Theresa May’s withdrawal plan and took control of the process.

Today, the Commons is expected to heavily reject a no-deal outcome and tomorrow seek to delay Brexit beyond March 29 in further votes. But, as one Scottish Tory MP put it, the way ahead has "never been more uncertain".

The Prime Minister announced Conservative MPs would be allowed a free vote on the no-deal issue, admitting she had "personally struggled with this choice" but believed the best way to leave the EU was "in an orderly way" with a deal.

She noted: "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."

But it is thought if Mrs May had tried to whip her MPs to keep a no-deal outcome on the table, she would have lost a raft of ministers.

A Labour spokeswoman said: "Allowing a free vote on no-deal shows Theresa May has given up any pretence of leading the country. Once again, she's putting her party's interests ahead of the public interest."

On another dramatic day at Westminster, MPs voted by 391 to 242 against the Prime Minister’s deal, despite her assurance that new agreements reached with Jean-Claude Juncker, the European Commission President, in Strasbourg on Monday night would ensure the UK could not 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 exit day.

Some 75 Conservative MPs rebelled to vote against the deal, including Ross Thomson, the Tory MP for Aberdeen South, while just three Labour MPs and four independents joined the 235 Tories who backed it.

One Scottish Conservative MP expressed disbelief at the actions of some of his Brexiteer colleagues, saying he was “disgusted” by them.

He told The Herald: “The 75 Conservative votes against the revised agreement are absolutely flabbergasting to me. Too many of my colleagues are English Nationalist ideologues with whom I find I have little in common. They are neither Conservatives nor Unionists.”

He added that rejecting Mrs May’s plan in this way “feeds the Nationalist agenda,” with the SNP wanting a political crisis and a no-deal hiatus to “give them the platform they need for their second independence referendum”.

Nicola Sturgeon, who spoke to the PM before the vote, said Mrs May and her ministers “should be hanging their heads in shame” as the outcome had been entirely predictable.

“If they had been prepared to listen at any stage and engage constructively instead of simply pandering to Brexit extremists, they could have avoided it,” declared the First Minister.

She claimed the UK Government had now “effectively ceased to function” and had failed to turn the 2016 referendum result into a workable or a deliverable plan to leave the EU.

"Ruling out no-deal and extending Article 50 would stop the clock on Brexit and enable another referendum on EU membership to be held. We will support any such referendum, provided it has the option to remain in the EU on the ballot paper.”

The FM added: "Scotland's needs and voice have been ignored by the UK Government throughout the Brexit process and today a handful of DUP MPs held more sway over Scotland's future than our own national Parliament; that demonstrates more clearly than ever that the case for Scotland becoming an independent country has never been stronger."

In a heavily packed Commons chamber, the PM, struggling with a croaky voice, said she still believed leaving with a deal was the best option for Britain and insisted, despite the two heavy Commons defeats, "the deal we've negotiated is the best and indeed the only deal available."

She stressed: "Let me be clear. Voting against leaving without a deal and for an extension does not solve the problems we face.

"The EU will want to know what use we mean to make of such an extension and this House will have to answer that question. Does it wish to revoke Article 50? Does it want to hold a second referendum? Or does it want to leave with a deal, but not this deal?

"These are unenviable choices. Thanks to the decision that the House has made this evening, they are choices that must now be faced."

An extension of Article 50 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.

Following the vote, a spokesman for Donald Tusk, the European Council President, insisted the EU had done all it could to reach an agreement. “If there is a solution to the current impasse it can only be found in London."

He explained if there were a “reasoned request” for an extension, then the EU27 would decide on it by unanimity but made clear there had to be a “credible justification” for it.

The spokesman added: "With only 17 days left to March 29, today's vote has significantly increased the likelihood of a no-deal Brexit.”

Business groups expressed dismay at the turn of events. The Confederation of British Industry said: “It’s time for Parliament to stop this circus. This must be the last day of failed politics. Jobs and livelihoods depend on it.”

Earlier in the day in Downing St, Cabinet gave its approval to Mrs May's package. The PM told her colleagues: "Today is the day. Let's get this done."

Yet the momentum moved sharply against the PM shortly afterwards when Geoffrey Cox, the Attorney General, released formal legal advice that acknowledged the changes secured by the PM from Brussels "reduce the risk" that the backstop would be permanent but did not remove it altogether.

The so-called “Star Chamber” of lawyers convened by the Brexit-backing European Research Group declared three new documents agreed in Strasbourg failed to deliver the legally-binding changes demanded by the Commons.

And the Democratic Unionist Party - which props up Mrs May's minority administration in the Commons - said its 10 MPs would vote against the latest deal as "sufficient progress has not been achieved at this time".

With husband Philip watching from the Commons gallery, the PM warned MPs that "Brexit could be lost" if they gave her deal the thumbs-down again.

But she met a wall of hostility from her own party as well as the opposition parties. The 75 Tory MPs voted against her deal along with 238 Labour, 35 SNP, 11 Liberal Democrats, 10 DUP, four Plaid Cymru, 17 Independents and Green Party MP Caroline Lucas.

Jeremy Corbyn told MPs: "After three months of running down the clock the Prime Minister has, despite very extensive delays, achieved not a single change to the Withdrawal Agreement.

"Not one single word has changed. In terms of the substance, literally, nothing has changed."

His colleague Sir Keir Starmer, the Shadow Brexit Secretary, said the Government's strategy was now "in tatters".

Boris Johnson, the former Foreign Secretary and Brexit figurehead told the Commons Mrs May and Mr Cox had "sowed an apron of fig leaves that does nothing to conceal the embarrassment and indignity of the UK."

Tory backbencher John Lamont said the vote had been lost because ardent Leavers who wanted no-deal and ardent Remainers, who wanted to reverse Brexit, joined forces. “A refusal to compromise by these two groups now means the future path has never been more uncertain,” said the Borders MP.

His Conservative colleague Charles Walker, Vice-Chairman of the 1922 Committee of backbench Tories, warned defeat in the second "meaningful vote" would lead to a general election.

"If it doesn't go through tonight, as sure as night follows day, there will be a general election within a matter of days or weeks. It is not sustainable, the current situation in Parliament."