The EU's Brexit negotiator has said the European Union will not renegotiate the deal struck with Britain regarding the trading position in Northern Ireland as to do so would only lead to instability and uncertainty.

Maroš Šefcovic said in a speech 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.

However, the DUP has reacted angrily to Mr Šefcovic's recent comments and described them as "belligerent".

The party said it had repeatedly issued warnings and "gave space" for issues surrounding the protocol to be ironed out, adding "this cannot go on".

Party MP Gavin Robinson also suggested that describing the protocol as solely a unionist problem is "mistaken and foolish".

His party leader Jeffrey Donaldson accused Mr Šefcovic of dismissing the concerns of unionists.

Mr Donaldson has threatened to pull out of Stormont and spark an election if significant changes are not made to the protocol in the coming weeks.

He said the political institutions could only work if they had the support of both unionist and nationalists.

"The EU needs to move and move quickly to address the concerns of unionists," he said.

He said negotiators needed to "get down to brass tacks to start dealing with and addressing and solving the difficulties that this protocol is causing."

"The Irish Sea border is the problem and the government needs to act to address it."

He said he was confident that compromises could be reached that would restore NI's place within the UK's internal market and protect the integrity of the EU's single market.

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.

The UK has since said the arrangement is not working and wants it changed.

Mr Šefcovic 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.

Mr Šefcovic was speaking at an event at Queen's University, billed as the main public event of his two-day visit.

His arrival at the university was met by a small loyalist protest.

Additional reporting Reuters, PA