Brexit Secretary David Davis' decision to include the provision in the EU (Withdrawal) Bill has also made the maximum facilitation or "max fac" option - which would see new technology used to deal with cross-border trade - "unlawful".
Theresa May was forced into a major compromise yesterday when she had to agree to give parliament a greater role in Brexit negotiations to avert a defeat at the hands of rebels from her own party who want to keep close European Union ties after Britain leaves.
They said: "We have not, and will not, agree to the House of Commons binding the government's hands in the negotiations".
On Tuesday night MPs passed a little-noticed amendment to the EU Withdrawal bill, which many MPs now believe could effectively force Britain to stay in the single market after Brexit.
Davis agreed to remain in place after receiving a guarantee the arrangement would last just a year and held a short meeting with EU Brexit chief Michel Barnier in Brussels today.
Soon after, Mr Buckland intervened on Mr Grieve to suggest talks over a compromise deal.
"They're even whispering during Prime Minister's Question Time", he said of the cabinet ministers sitting opposite him in the Commons.
De Gea wants public apology from Spain PM
It remains to be seen whether or not will he make the much-anticipated big-money move to Madrid this summer. Come what may, I'll be the same. "I just want to be 100 percent focused on the World Cup".
"The prime minister conceded she understood points A and B of the Dominic Grieve amendment and there will be further discussions on C, with a view on bringing the amendment in the House of Lords, so that will be discussed further", she said. The victory was Pyrrhic, as the government's earlier climbdown all but ensures MPs will have an increased say on the terms of any deal.
- PM avoids damaging "meaningful vote" defeat through new concessions. "The EU will have no incentive to give us a deal because it can pass to parliament to keep us back in and extend article 50", one senior figure on the Brexiteer side told me. "It would be total, abject surrender against the Brexiteers and what the country voted for".
The government was putting a combative spin on the concessions Tuesday evening: "The Brexit Secretary has set out three tests that any new amendment has to meet - not undermining the negotiations, not changing the constitutional role of Parliament and Government in negotiating global treaties, and respecting the referendum result", a spokesperson for the Brexit department said in a statement.
British Prime Minister Theresa May faces another day of Brexit compromise at Westminster.
Morgan admitted there was a part of the Grieve amendment that "does go further" than the prime minister was prepared to accept but said they had not been played.
"If she has given too much away I think there will be real anger towards her".