A Christian political campaigner has said the Government re-working the terms of the Withdrawal Agreement breaks international law.
The Financial Times reported the Government is planning to table legislation which would override key elements of the Brexit deal which sealed the UK's departure from the EU in January.
The move raised concerns that the Government could walk away from the Northern Ireland protocol - intended to ensure that there is no return of a hard border with the Republic - if the talks on a free trade deal fail.
Mike Buckley, who leads the political leadership programme for Christians on the Left, told Premier: "The government have now said that they want to rip up parts of the Withdrawal Agreement, which is against international law...it's effectively saying we want to be a petty criminal in international law terms. So it's not good for our relationship with the European Union. But it's also not good if we want to have a trade agreement with any other country because every other country in the world now will look at us and think these guys can't be trusted anymore."
The suggestion the UK could possibly undermine an international treaty and use Northern Ireland as a bargaining chip was greeted with anger and dismay among key figures in Ireland and mainland Europe.
The EU's negotiator Michel Barnier said he would be seeking clarification about the UK's plans.
However, Environment Secretary George Eustice said the Internal Market Bill, due to be published on Wednesday, was simply designed to tie up some "loose ends" where there was a need for "legal certainty".
He insisted that the Government remained committed to the principles of the deal, which will see customs checks on some goods moving from the rest of the UK to Northern Ireland.
"What we are talking about here is what type of administrative customs processes you might have for goods that might be at risk of entering the EU single market - going from GB to Northern Ireland," he told the BBC Radio 4 Today programme.
"These are important but minor technical details. The principle behind the protocol of checks on some of those goods entering through Northern Ireland ports is in the Northern Ireland protocol and we remain committed to it."
Buckley told Premier he doubts the government's strategy will be successful.
"What they're trying to do is put pressure on the EU to say, if you don't agree to our terms with a future trade agreement, we'll rip up the agreement we've already got," he said.
"It won't work, because the EU will take no notice whatsoever. It's a bit like a petulant child having a tantrum in a classroom. The teacher is not suddenly going to turn around and say, 'Oh, yes, well you're right'. They will just continue trying to work with the petulant child."
The row erupted as Mr Johnson set a five-week deadline for talks with the EU on a post-Brexit free trade deal to either reach agreement or for both sides to accept there will be no deal when the current transition period ends at the close of the year.
In a statement ahead of the resumption of talks in London on Tuesday, the Prime Minister said that if there was to be an agreement it needed to be in place by the time of the next EU summit on 15th October, and that no-deal would still be a "good outcome" for the UK.
Listen to Premier's interview with Mike Buckley here: