THERESA May has suffered another humiliating defeat in the House of Lords over her plans to take the UK out of the European Union.

Peers, including former Conservative deputy prime minister Lord Heseltine, backed an amendment calling for MPs to have a “meaningful” say on any exit deal with Brussels.

The Tory Government will try to overturn the change in the Commons.

But Tory MPs are being urged to defy Mrs May’s to defend the principle of parliamentary sovereignty.

The Prime Minister has promised the Commons a vote on the final ‘divorce settlement’ with the EU.

But critics say the pledge is meaningless because she has also warned MPs that they will have just two options - to either “take it or leave it”.

Opponents want to be able to tell Mrs May to go back to the EU and negotiate a better deal.

But Tory insiders argue that would weaken the UK’s hand in talks and lead to an even worse agreement.

Lord Heseltine told peers that withdrawal from the EU would be fiendishly complicated and that they had to ensure Parliament had a “critical role in determining the future that we will bequeath to generations of young people.”

But former chancellor Lord Lawson of Blaby branded the move “mischievous” as he urged the Lords to reject it.

Another fellow Tory, the former Scottish Secretary Lord Forsyth, accused some peers of a “confection” designed not to give MPs a say on the final outcome but to overturn the result of the EU vote.

At the weekend Mrs May had warned peers that if they backed the amendment they risked handing other EU countries an incentive to give the UK a bad deal.

But many in the Lords were emboldened by claims that the courts could intervene if Mrs May fails to give MPs a substantive vote.

The Supreme Court has already been forced the Tory leader to bring the Brexit Bill before the Commons, after she attempted to bypass parliament altogether.

In the end peers voted by 366 votes to 268, a majority of 98, for parliament to have to agree the outcome of Brexit talks, even if there is no deal.

Last week peers voted by a similar margin, 358 to 256, for another amendment demanding that EU citizens be told that they can stay after Brexit.

Mrs May has protested that she cannot give that guarantee until other EU countries make a similar pledge to UK nationals.

But critics have urged her to make a unilateral declaration.

After the vote the Brexit Secretary David Davis said that the result had been “disappointing” and pledged to fight on.

The Brexit Bill had a “straightforward purpose”, he said, “ to enact the referendum result and allow the Government to get on with negotiating a new partnership with the EU.

“It is clear that some in the Lords would seek to frustrate that process, and it is the Government’s intention to ensure that does not happen.

“We will now aim to overturn these amendments in the House of Commons.”

Former deputy prime minister Nick Clegg said that peers had “rightly stood up for parliamentary sovereignty and refused to write the Government a blank cheque.”

He called on MPs to “find the nerve to do the same ... our elected representatives must be offered more than just a bad-deal-or-no-deal ultimatum at the end of the negotiations – the parliamentary equivalent of being asked whether you would prefer to lose an arm or a leg.

“I would urge MPs of all parties, including Brexiters who campaigned to Leave on the basis of parliamentary sovereignty, to stop Parliament being neutered.”

Earlier peers voted down a call a second referendum.

The Liberal Democrats have called for the outcome of Brexit negotiations to be put to voters not politicians.

But that call was rejected by the Lords.