Brexit: Hardline anti-EU Tories deliver second major blow to May's revised deal as they urge MPs to reject plan

Eurosceptic 'Star Chamber' says prime minister's plan fails to meet government's own tests

Theresa May's hopes of getting her Brexit deal through parliament have been dealt another devastating blow after a committee of leading Tory Eurosceptics recommended that MPs reject the plan.

The European Research Group's (ERG) legal panel, set up to analyse the revised deal, said the prime minister's updated plan did not meet the government's own tests.

The verdict, which is expected to be highly influential among Tory MPs, means the deal is all but certain to be rejected for a second time when the Commons votes on it tonight, dealing what could be a fatal blow to Ms May's Brexit strategy.

Veteran Tory MP Sir Bill Cash, who chaired the ERG "Star Chamber", said: "In the light of our own legal analysis and others we do not recommend accepting the government's motion today."

Ms May had hoped to convince Eurosceptics to back her deal after agreeing three new documents during frantic last-minute talks with EU leaders in Strasbourg last night. They make clear that the controversial Irish backstop, which would see the UK join a customs union with the EU if no other deal is agreed, is designed to be temporary. The government also published a unilateral statement outlining how it could leave the backstop.

But in its assessment of the new concessions, the committee said: "Yesterday's documents considered individually and collectively do not deliver 'legally binding changes' to the withdrawal agreement or the [Northern Ireland] Protocol. They fail to fulfil the commitment made by government to the House in response to the Brady amendment 'to obtain legally binding changes to the withdrawal agreement'.

"They do not provide any exit mechanism from the Protocol which is under the UK's control."

The ERG set up the committee, which consisted of Brexiteer MPs with legal experience, to analyse whatever new concessions Ms May secured from the EU.

Its verdict came shortly after the prime minister suffered another blow when Geoffrey Cox, the attorney general, published his own legal opinion saying the "legal risk" of the UK remaining trapped in a customs union with the EU "remains unchanged".

In a written ruling published shortly before he delivered an oral statement in the Commons, Mr Cox said the new documents agreed in Strasbourg "reduce the risk that the United Kingdom could be indefinitely and involuntarily detained" if the EU fails to use its "best endeavours" to negotiate an alternative arrangement.

But he warned that "the legal risk remains unchanged" if no agreement can be reached due to "intractable differences", saying in this case UK would have "no internationally lawful means" of leaving the backstop without EU agreement.

Ms May had hoped that the last-minute concessions she secured in Strasbourg would be enough to convince Tory Eurosceptics and her Commons partners in the DUP to back her plan.

But the DUP joined the ERG in saying it would vote against the revised deal.

A spokesperson said: "Having carefully considered the published material as well as measuring what has been achieved against our own fundamental tests, namely the impact of the backstop on the constitutional and economic integrity of the Union of the United Kingdom, it is clear that the risks remain that the UK would be unable to lawfully exit the backstop were it to be activated."

The party's Westminster leader, Nigel Dodds, told the Commons: "We know already from the Irish government and others what they see as the ultimate destination for Northern Ireland - the backstop is the bottom line.

"From what the attorney general is saying today, provided there is no bad faith, the fact is that Northern Ireland and the rest of the United Kingdom could be trapped if it's a question that the EU does not agree with the United Kingdom to a superseding agreement."