SNP: May's Brexit deal failure shows emperor has no clothes
Attorney General Geoffrey Cox earlier confirmed the UK could still get trapped in the backstop.
Theresa May's last-minute changes to her Brexit deal "fall very short" of what was promised and show "the emperor has no clothes", the SNP has said.
The party's justice spokeswoman Joanna Cherry said the updated legal advice from Attorney General Geoffrey Cox on the UK's agreement with Brussels had "burst his party's political bubble".
She was replying to Cox in the House of Commons as he attempts to persuade MPs the changes May secured at the 11th hour "reduce the risk" Britain could be trapped indefinitely in the controversial Irish backstop.
But in a blow to the Prime Minister, the Attorney General also confirmed the alterations do not remove the risk of the UK becoming locked into the backstop - a provisional UK-wide customs arrangement with the EU to prevent a hard border in Ireland - which is a key demand of Tory Brexiteers.
Cherry said the UK Government had failed to deliver, telling MPs: "The emperor has no clothes. None at all, not even a codpiece."
The Attorney General's legal opinion came after the Prime Minister's dash to Strasbourg on Monday night to agree new elements of her deal with European Commission president Jean-Claude Juncker.
They announced a new "joint instrument", carrying the same legal weight as the original Withdrawal Agreement, promising to seek alternative arrangements to avoid the need for a backstop by the end of the Brexit transition period in December 2020.
The pair also added a "supplement" to November's Political Declaration making clear they will seek to do a deal on their new trade and security relationship swiftly.
Alongside these documents was a "unilateral declaration by the UK" which sets out "sovereign action" by which Britain could seek to have the backstop removed if the EU acted in bad faith.
But Cox advised ministers that the "the legal risk" of getting caught in the arrangement remains "unchanged".
Cherry said: "I have respect and sympathy for the Attorney General.
"The role of the law officer is not an easy one, particularly when he or she is a party-political appointment but must nevertheless from time to time burst his party's political bubble in the interests of professional integrity and independent advice.
"And make no mistake: that is what the Attorney General has done today. Because, Mr Speaker, today the emperor has no clothes. None at all, not even a codpiece...
"These measures... fall very short of what was promised to the ERG, which I'm sure will not have been lost on them or their lawyers."
She added: "Does he agree with me that in fact nothing has changed and what the Prime Minister promised, she has yet again failed to deliver?"
The Attorney General responded that his legal advice provided a "clear pathway" for the UK to suspend the backstop if it could prove the EU had acted in bad faith by taking the country's case to an arbitration panel.
However, in a further blow to May's deal, leading Tory and DUP Eurosceptics have said they would not recommend MPs vote for it.
The so-called "star chamber" of lawyers convened by the ERG group found that the legally-binding changes the Commons demanded have not been delivered.