Legal advice provided to the Cabinet on Theresa May’s Brexit deal has warned it could result in the UK becoming stuck for many years in “protracted and repeating rounds of negotiations” with no lawful power to exit.
And it made clear that Brussels could apply to an arbitration panel for Northern Ireland to remain in the EU customs area while the rest of the UK left.
The six-page document by Attorney General Geoffrey Cox was released to MPs a day after the House of Commons found the Government in contempt of Parliament for trying to keep it secret.
Democratic Unionist Party leader Nigel Dodds described it as “devastating” and said it made clear that the proposed backstop arrangement for the Irish border was “unacceptable” and must be defeated.
The Scottish National Party’s leader in Westminster, Ian Blackford, called on Mrs May to take responsibility for “concealing the facts on her Brexit deal” from MPs and the public.
But Mrs May rejected the claim, insisting the document contained the same information as a shortened statement made to MPs by Mr Cox earlier this week.
Shadow Brexit secretary Sir Keir Starmer said that the 33-paragraph document revealed “the central weaknesses in the Government’s deal”.
Mr Cox found that the protocol setting out the terms of the backstop “does not provide for a mechanism that is likely to enable the UK lawfully to exit the UK-wide customs union without a subsequent agreement”.
“This remains the case even if parties are still negotiating many years later and even if the parties believe that talks have clearly broken down and there is no prospect of a future relationship agreement,” he added.
Under the arrangements, “for regulatory purposes, GB is essentially treated as a third country by NI for goods passing from GB into NI”, he said.
And he said that – despite assurances from both London and Brussels that it is intended to be temporary – the protocol would “endure indefinitely” under international law until another agreement takes its place.
The UK would have no legal means of compelling the EU to conclude any such agreement.
The Attorney General warned: “In the absence of a right of termination, there is a legal risk that the United Kingdom might become subject to protracted and repeating rounds of negotiations.
“This risk must be weighed against the political and economic imperative on both sides to reach an agreement that constitutes a politically stable and permanent basis for their future relationship.
“This is a political decision for the Government.”
Mr Cox’s advice stated that, if Brussels felt that negotiations on a trade deal had broken down or were taking too long, it would be able to apply to the arbitration panel for Britain to be removed from the customs union while Northern Ireland remains – effectively creating the border in the Irish Sea, which Mrs May has said no prime minister could accept.
But the Attorney General said it was “extremely difficult to see” the five-member panel being prepared to make such a political decision unless both sides agreed on it.
He also noted that the backstop arrangement would be “enormously complex” for the EU, requiring “considerable resources”, meaning Brussels would come under pressure – especially from Dublin – to bring it to an end.
“Given the lack of any effective means of termination, it is to these very real – albeit unquantifiable – factors, among others, that the UK may have to trust in seeking a satisfactory outcome,” he said.
Sir Keir said: “Having reviewed the Attorney General’s legal advice, it’s obvious why this needed to be placed in the public domain.
“All week we have heard from Government ministers that releasing this information could harm the national interest. Nothing of the sort.
“All this advice reveals is the central weaknesses in the Government’s deal.
“It is unthinkable that the Government tried to keep this information from Parliament – and indeed the public – before next week’s vote.”
Green MP Caroline Lucas questioned Mr Cox’s claim earlier this week that the advice should not be published “in the national interest”.
“On Monday the Attorney General told MPs that it would be ‘contrary to the national interest’ to release his legal advice of November 13,” said Ms Lucas.
“That legal advice consists of just 33 paragraphs. Perhaps the Prime Minister can tell us which paragraphs breach the national interest?”
Ms Lucas said it was “weird” that the Cabinet was not provided with formal legal advice on the backstop until the very day that the Commons voted for it to be released.
To the surprise of some MPs, Labour leader Jeremy Corbyn chose not to use any of his six PMQs questions to put Mrs May on the spot over her three defeats over Brexit in the Commons on Tuesday.
Mr Cox said the decision to make his legal advice available to MPs by placing it in parliamentary libraries was “exceptional” and did not set a precedent for any future release of law officers’ advice.
He said the use of the arcane parliamentary procedure of a humble address to the Queen to force the release of the document created “constitutional tensions” which “are not themselves conducive to the proper conduct of public affairs”.