Attorney General Geoffrey Cox was accused of trying to "hide behind convention" in a bid to prevent publication of Brexit legal advice given to Cabinet.
Shadow attorney general Nick Thomas-Symonds told the Commons that the Government was seeking to avoid the publication of legal advice for "fear of the political consequences".
He said: "For the sake of our economy, our jobs and our futures all possible information should be made available to members of this House.
“The Government should do the right thing and make this full advice available, with so much at stake for all our constituents, with eight days to go before the vote on the deal this House and this country deserves better from this Government."
Cox responded saying MPs had "far better" than advice that "may or may not" have been given to the Government as they could ask him.
The Attorney General was answering questions in the House of Commons following the publication of a legal summary on Theresa May's Withdrawal Agreement.
'Unless it is superseded'
The summary states that the Irish backstop would continue to apply "unless and until it is superseded" by a subsequent agreement.
The 43-page Legal Position On The Withdrawal Agreement, released on Monday afternoon, states: "The main provisions of the Protocol come into force from the end of the implementation period (31 December 2020 - see Article 185 of the Agreement) in the event that a subsequent agreement is not in place by then, and the Protocol will continue to apply unless and until it is superseded, in whole in or part, by a subsequent agreement establishing alternative arrangements (Article 1(4), and the fifth recital in the preamble)."
But if the implementation period is extended then the backstop will not apply until after the end of that period, the paper states.
"However, if the implementation period is extended in accordance with Article 3 of the Protocol and Article 132 of the Agreement, then the Protocol will not start to apply until after the end of that extended period. Certain provisions, relating to preparatory work or the obligation to use best endeavours to conclude an agreement to replace the Protocol, come into force immediately on the coming into force of the Agreement."
SNP Home Affairs spokeswoman Joanna Cherry, a QC, asked whether there was anything to prevent the backstop becoming a permanent arrangement.
The Attorney General agreed there was nothing in law to stop this but such an agreement based on Article 50 would be "highly vulnerable to legal challenge" and therefore, in his legal opinion, unlikely.
He said: "If negotiations irretrievably broke down it would de facto become permanent and it would therefore fall to be seriously challenge-able in the Court of Justice of the European Union for being invalid.
"That legal certainty by itself is sufficient to promote the EU to do a deal with us."