Theresa May’s hopes of winning over Eurosceptic MPs to her Brexit deal were dealt a sizeable blow on Tuesday by a legal opinion from her attorney-general.
Geoffrey Cox warned that the risk of the UK being trapped in a so-called backstop arrangement to avoid a hard Irish border after Brexit remained “unchanged”, despite new assurances about the prime minister’s withdrawal agreement that were published on Monday evening by the EU and Britain.
Mr Cox’s legal advice had been seen by ministers as a key tool for persuading Eurosceptic Conservatives and the Democratic Unionist party to back Mrs May’s deal in a “meaningful vote” by the House of Commons on Tuesday evening.
But a group of lawyers advising the pro-Brexit European Research Group of Tory MPs said after the release of Mr Cox’s opinion that the government had failed to meet its own tests and recommended voting against Mrs May’s deal.
Nigel Dodds, the Westminster leader of the DUP, also appeared to take a dim view of the advice, noting that the UK “could be trapped” in the Irish backstop in certain circumstances.
Mrs May suffered a record Commons defeat in January when MPs last voted on her Brexit deal, with the ERG and the DUP both opposing it.
Mr Cox concluded in previous legal advice last year that the backstop could endure “indefinitely”, enraging Eurosceptics who fear the arrangement would lock Britain into a permanent customs union with the EU and prevent the UK striking trade deals after Brexit.
Some MPs had expected him to change his stance after the latest negotiations on Mrs May’s Brexit deal between the UK and Brussels, in which he was a key player.
In a three-page letter to Mrs May published on Tuesday, Mr Cox said the new Brexit assurances “reduce the risk that the United Kingdom could be indefinitely and involuntarily detained” in the Irish backstop because of bad faith on the EU’s part.
But he added that “the legal risk remains unchanged” that, if there were “intractable differences” between the UK and the EU, rather than bad faith by the bloc, Britain would have “no internationally lawful means of exiting” the backstop without the bloc’s agreement.
David Davis, the former Brexit secretary, said earlier that if Mr Cox was “at all equivocal” about the legal position, the deal would be defeated again in the Commons.
The pound fell 1 per cent against the US dollar, to $1.3020 just after the release of Mr Cox’s letter, more than wiping out a rally late on Monday after Mrs May unveiled the Brexit assurances with the EU. Sterling had traded as high as $1.3288 after Monday night’s New York close.
Members of the government pointed to the more upbeat parts of Mr Cox’s advice, including his “political judgment” that it was “highly unlikely” that an alternative to the backstop would not be found. But one Downing Street official, referring to Tuesday’s vote, said: “We’ve got a big selling job on our hands.”
Mr Cox has become an influential figure in the Brexit process, despite being little-known in British politics until his appointment as attorney-general last year.
In an interview with the Mail on Sunday last week, he insisted he would never deliver politically-convenient advice to the government.
“I have been a barrister for 36 years, and a senior politician for seven months,” he told the newspaper. “My professional reputation is far more important to me than my reputation as a politician.”
The legal documents about the Brexit assurances, presented by the EU and the UK on Monday evening, fell short of a parliamentary amendment backed by MPs in January that said the backstop should be “replaced”.
The documents did not provide a fixed end date for the backstop, or a unilateral exit mechanism, which Mrs May had subsequently suggested could be negotiated.
Eurosceptics had earlier urged Mrs May to postpone the meaningful vote on her Brexit deal to give them more time to study the last-minute compromise struck by Mrs May and Jean-Claude Juncker, European Commission president, in Strasbourg on Monday evening.
Jacob Rees-Mogg, chair of the European Research Group, which represents about 80 pro-Brexit Conservative MPs, told the BBC that it would be “better to have the vote tomorrow”.
However, the government’s ability to postpone the vote is constrained by the fact that the date was endorsed by the Commons in a parliamentary motion last month.