Peers say Theresa May is heading for another thumping Brexit defeat in the House of Lords, to prevent her crashing Britain out of the EU with ‘no deal”.

Both Labour and the Liberal Democrats believe they comfortably have the numbers to win a crunch vote next Tuesday to ensure Parliament has a “meaningful vote” on the Prime Minister’s exit terms.

Crucially, a new amendment to the Article 50 bill would bind Ms May to obtain Parliament’s approval to leave the EU “without an agreement as to the applicable terms”.

It would prevent her unilaterally carrying out her threat to walk away if EU leaders offer only a ‘bad deal” – leaving Britain out of the EU on punishing World Trade Organisation (WTO) rules.

The determination of peers has been bolstered by the commanding majority that defeated the Government this week over the future rights of EU citizens in the UK.

A Labour source in the Lords told The Independent: “Given the scale of the previous defeat – and the building up of a cross party campaign on this issue – we are again likely to see the government defeated handsomely'.

And Tim Farron, the Liberal Democrat leader, said, emphatically: “The Government will be defeated again.

“Theresa May must accept the strength of feeling both in the Lords and across the country. She has already faced a humiliating defeat on the Brexit bill and will face more if she refuses to make concessions.”

The amendment has been tabled by Labour, with support from the Lib Dems and two prominent crossbench – or independent – peers, raising the likelihood it will be passed.

The likelihood of Britain “going over the cliff-edge” appears to be growing, after Brexit Secretary David Davis told Cabinet colleagues this week to prepare for it – although he claimed it was still an “unlikely scenario”.

WTO rules would mean hefty export tariffs on, for example, dairy products (36 per cent), cars (ten per cent), food and drink (20 per cent) and clothing and textiles (10-20 per cent).

But this ultimate hard Brexit could also see billions of pounds having to be spent on new IT systems for customs declarations, on holding facilities at big ports and on a new immigration system to process applications for work permits.

The British Chambers of Commerce has called for Brexit to be delayed if necessary, to sort out a trade deal – and the CBI has branded the Prime Minister “not only wrong but irresponsible” to threaten to walk away.

Defeat next week would see growing pressure on Remain-backing Conservative MPs to join forces with the opposition parties to prevent the amendment being thrown out in the Commons.

Just seven rebelled when the controversy was voted upon last month – but others were angry at alleged dirty-dealing by Downing Street on the exact nature of the “meaningful vote”.

No 10 promised the vote would take place before any deal reaches the European Parliament, but was unclear if it would take place if there were “no deal” – and the assurances were verbal only.

On that occasion, Ms May won with a majority of 33, suggesting at least 25 Tory rebels will be needed when the clash returns to the Commons, probably on 13 March.

The Lib Dems say they are preparing for an all-night stand-off the week after next, when MPs and peers will also go into battle over EU citizens’ rights.

“If that means pizza and food delivery at 3am then so be it. We have plans in place for sleeping bags and beds,” a party source said.