Theresa May warned that Brexit is 'heading back to the courts' after she refuses to give MPs a ‘meaningful vote’

‘If they don’t follow proper constitutional process, there will be litigation – and that litigation will hold matters up’, former Tory Attorney General Dominic Grieve warns

Downing Street has squashed speculation the Prime Minister could trigger Article 50 tomorrow (House of Commons)

Theresa May has been warned that Brexit is heading back to the courts after she refused to give MPs a “meaningful vote” on any final deal.

A senior Conservative insisted the law will not allow the Prime Minister to take Britain out of the EU without Parliament backing the outcome of the exit talks.

Dominic Grieve, the former Conservative attorney general, said: “I can promise them, if they don’t follow proper constitutional process, there will be litigation – and that litigation will hold matters up.”

Vowing not to support the Government, he added: “I am afraid I’m not prepared to follow processes which appear to me to be, frankly, deranged.”

The warning follows the earlier Supreme Court ruling that ministers cannot remove rights from British citizens without the authority of Parliament.

As expected, the Commons threw out an amendment passed by the House of Lords to ensure Parliament has the final say over the nature of Britain’s withdrawal from the EU.

Not a single Conservative MP voted with the Opposition parties – despite Brexit Secretary David Davis failing to offer any concession on the vote on any final deal – allowing the Government to win by 331 votes to 286, a majority of 45.

Mr Davis had been expected to pledge a vote even if Ms May fails to strike a deal – to ease concerns that Britain could crash out of the EU with no agreement – but gave no concessions.

Instead, he won over some potential rebels by arguing that “tying the Government’s hands” would hinder hopes of a successful outcome.

Mr Davis also insisted guaranteeing MPs the opportunity to vote down the outcome of the negotiations would make EU leaders more likely to refuse to offer a good deal.

And he added: “Whilst this has been badged as a meaningful vote, the reality is there are some who would seek to use this to overturn the result of the referendum.”

But Mr Grieve refused to vote with the Government, telling Mr Davis: “Somebody’s got to put down a marker that we have to follow proper process in the way in which we carry out Brexit.”

And another pro-EU Tory, Anna Soubry warned leaving the EU with no deal could spell “the break-up of the United Kingdom”, with border controls reintroduced in Ireland and Scotland voting for independence.

“Falling off the cliff-edge is the worst possible outcome for the people of this country – that is the one thing we must make sure doesn’t happen,” she said.

The win for the Government came just minutes after the Lords’ call for 3m EU citizens in Britain to be given a unilateral guarantee that they can stay after Brexit was also easily defeated.

Within minutes, Labour said it would concede defeat in the House of Lords, rather than “ping” the Bill back to the Commons for further debate.

That guarantees the Government will win further votes in the Lords later tonight – allowing the European Union (Notification of Withdrawal) Bill to receive Royal Assent early tomorrow.

However, No 10 has squashed speculation that she could trigger Article 50 as early as tomorrow, signalling that will now happen in the last week of March.