A member of the DUP has described comments by a senior European Union official rejecting British calls for a post-Brexit trade agreement to be renegotiated as "belligerent", "mistaken" and "foolish".
Earlier, the EU rejected the British demand to renegotiate their deal governing the trading position of Northern Ireland, saying that to so would only lead to instability and uncertainty.
European Commission Vice-President Maros Sefcovic, who oversees post-Brexit EU relations with Britain, said in a speech on Friday that the Northern Ireland Protocol needed to be properly implemented and was not the cause of problems, but the only solution.
"A renegotiation of the protocol – as the UK government is suggesting – would mean instability, uncertainty and unpredictability in Northern Ireland," he said, according to the text of his speech at Queen's University in Belfast.
Under the protocol, Britain agreed to leave some EU rules in place in Northern Ireland and accept checks on goods arriving from elsewhere in the United Kingdom. London has since said the arrangement is not working and wants it changed.
However, responding to Mr Sefcovic's remarks, Gavin Robinson said: "For an EU vice-president to dismiss our warnings as 'rhetoric' is belligerent.
"This is not just a unionist problem. To describe it as such is to be mistaken and foolish."
This comes after the DUP signalled on Thursday that they would collapse powersharing in Northern Ireland within weeks if changes to the protocol are not delivered.
Speaking to the BBC Nolan Show on Friday, DUP leader Jeffrey Donaldson said he threatened to pull his ministers out of the Stormont executive because he feared negotiations between the EU and UK government over the protocol would be “dragged out” for years.
“I want to get a solution here to the problems that have arisen from this protocol and the harm that it does on a daily basis to Northern Ireland," he said.
“I am hoping that within weeks we will get solutions that will help us to remove the Irish Sea border and restore our place within the UK internal market."
Mr Donaldson said he was "encouraged" by a meeting he had with Mr Sefcovic in Belfast yesterday. "I think there is now a realisation that we can’t go on dragging this out interminably," he added.
Separately in his address on Friday, Mr Sefcovic said the EU was committed to working with Britain to overcome difficulties, but added any solutions could only minimise the effects of Brexit, not entirely remove them, given London's choice to leave the EU single market and customs union.
The commissioner said the two sides should continue discussions to limit the impact of the protocol on everyday life in Northern Ireland, while maintaining its special access to the EU's internal market.
But the focus of these discussions should be issues that mattered most to Northern Irish people, he said, not British requests such as to remove the oversight role of the European Court of Justice.
"Doing this would effectively mean cutting Northern Ireland off the EU’s single market and related opportunities," he said.