Boris Johnson’s senior Brexit adviser has signalled that the next phase of talks with the EU will be tough.
David Frost, known as “the sherpa” on EU negotiations, said that the “intensified process” in discussions next week needed to be realistic.
He said the UK would not allow Brussels the right to hit back at changes in British law with tariffs.
The comments come after Prime Minister Boris Johnson insisted that the UK would reject an EU offer to extend the Brexit transition period beyond the end of the year.
In bullish language, Mr Frost insisted that UK sovereignty over laws, courts, and fishing waters was “not up for discussion”.
He also stated that what he called some of the EU’s more “unrealistic positions” will have to change in order to achieve progress.
He tweeted: “We will go to Brussels in good faith to engage with the EU’s concerns.
“This needs to be a real negotiation and some of the EU’s unrealistic positions will have to change if we are to move forward.
“We have noted carefully what the EU has said in recent days on this subject and look forward to discussing it.
“UK sovereignty, over our laws, our courts, or our fishing waters, is of course not up for discussion.
“Equally we do not seek anything which would undermine the integrity of the EU’s single market.
“I want to be clear that the Government will not agree to ideas like the one currently circulating giving the EU a new right to retaliate with tariffs if we chose to make laws suiting our interests.
“We could not leave ourselves open to such unforeseeable economic risk.”
Mr Frost said he was looking forward to the resumption of face-to-face talks in the wake of the coronavirus outbreak.
He said: “The next round of talks with the EU begins on Monday 29 June. This is the start of the intensified process.
“For the first time since March we will meet face to face, in Brussels. We look forward to welcoming the EU team to London the week after.
“These meetings will be smaller and focused on seeing whether we can begin to make genuine and rapid progress towards an agreement.”
The UK has a deadline of July 1 if it wants to extend the transition period beyond the end of the year.