THERESA May's chief Brexit adviser secretly warned her that the 'backstop' agreed in her deal with Brussels was a "bad outcome" for Britain, it has been reported.
In a letter to the prime minister, Oliver Robbins said the backstop, intended to prevent the return of a hard border with the Republic, would mean the imposition of regulatory checks between the north and the rest of the UK, according to The Daily Telegraph.
The disclosure will add to the pressure on the prime minister at the start of another difficult week as she battles to save her Brexit deal ahead of the crucial Commons vote on December 11.
The paper, which said it had been passed details of the letter by a "concerned minister", Mr Robbins said had advised there was no legal "guarantee" Britain would be able to exit the backstop, potentially leaving the UK tied to EU customs arrangements.
He was said to have written: "We should not forget that the backstop world, even with a UK-EU customs union, is a bad outcome with regulatory controls needed somewhere between GB and NI, serious and visible frictions and process between GB and the EU, and no security cooperation provided for."
The leak preceded demands for the government to release the full legal advice on the Withdrawal Agreement.
Meanwhile, MPs need to get their heads "out of the sand" and recognise Parliament will not support any Brexit option on the table, a Tory former Cabinet minister has said.
Justine Greening made the comments as she joined campaigners delivering a petition for another referendum to Downing Street.
She said she would vote against Theresa May's deal in the Commons next week, and instead called for a People's Vote on the final deal.
Ms Greening joined dozens of campaigners and MPs from three other parties to deliver petitions, signed by more than a million people, from the Independent newspaper's Final Say campaign as well as the People's Vote.
She told the Press Association: "I think that MPs need to take their heads out of the sand and recognise that Parliament isn't going to vote for any of the options on the table but in that case we can't just decide to disagree and go nowhere – we have a responsibility to find a route through for people in our country."
