Sir Keir Starmer has said the UK and EU need to negotiate to remove trade barriers and avoid a trade war, and accused Boris Johnson of not having read or understood the Brexit treaty.
The UK and EU are currently teetering on the brink of a sausage trade war as they argue over the implementation of the Northern Ireland Protocol and its Irish Sea border with Britain.
The Protocol means checks are carried out on British goods exported to Northern Ireland, which continues to follow some EU rules, to prevent a hard Irish border with EU member Ireland.
Mr Johnson has demanded fewer burdensome checks on British goods and argued that they pose a threat to the “territorial integrity” of the UK.
Sir Keir told LBC radio that the checks were “not the way forward” but added that “we can’t have this stand-off and both sides need to negotiate.”
“The Prime Minister said there wouldn’t be checks, that’s how he sold his deal,” he said. “He didn’t read it, didn’t understand it, or he didn’t tell us the truth about it when he said what it had in it.”
Sir Keir’s intervention comes after the looming sausage trade war dominated the G7 meeting in Cornwall with EU leaders such as Emmanuel Macron heaping pressure on Mr Johnson to cave to their demands.
Brussels has called on Britain to sign a Swiss-style veterinary agreement, which would mean Britain aligning with EU food safety and animal health rules.
The EU says this would remove the need for 80 per cent of checks in the Irish Sea but the UK has rejected any suggestion of dynamic alignment on sovereignty grounds.
A Labour source said: “We think that the PM should be pursuing serious solutions, such as a veterinary agreement, which could lower the barriers across the Irish Sea which his deal has created.”
On Sunday, Emily Thornberry, a member of the shadow cabinet, told Sky News, said: “I personally think that the Swiss model is probably the best one and we should just get on with it.”
The Government believes the EU is attempting to re-fight the Brexit negotiations through Northern Ireland. It wants Brussels to agree to a looser veterinary agreement, where the EU would deem UK rules as equivalent to their own.
Unless a veterinary agreement can be found by time a grace period in the protocol expires at the end of the month, British chilled meats such as sausages will be banned in Northern Ireland from July 1.
Brussels has warned it could retaliate with tariffs and other punishments if Mr Johnson unilaterally extends the grace period to protect sausage supplies to Northern Ireland.
It would be the third time the UK had overridden the Protocol, which Brussels says breaks international law.
DUP leader Edwin Poots told BBC Radio Ulster: "Ultimately the Protocol is the problem. Tinkering about at the edge of the Protocol is not the solution.”
He ruled out a potential Swiss-style deal as "anti-democratic" and said the "EU should not be imposing things which are anti-democratic in Western Europe".