UK shows 'bad faith' in post-Brexit talks, Irish PM says

"It is perfectly reasonable to look for ways to improve the operation of the protocol, but unfortunately what we have seen are bad-faith efforts to undermine a treaty freely entered into," Martin told MEPs.

He added, "we have actually seen efforts to block agreements or introduce new problems."

The UK government has been threatening to scrap parts of the deal that governs the trade relations between the UK and the EU and Northern Ireland, which has a land border with the bloc.

The EU has repeatedly warned the UK against making any unilateral moves, saying it would be a breach of international agreement, as Johnson himself signed the divorce deal, including the protocol.

The protocol was designed to square acircle: keep the land border seamless on the island of Ireland which is key to the 1998 Good Friday Agreement that brought decades of sectarian violence to an end.

At the same time, it also aims to keep the integrity of the EU's single market by creating customs checks in the Irish sea, between Northern Ireland and the rest of the UK.

Martin said that "no serious consideration" was given to the implications of the Brexit vote on Northern Ireland, which itself voted to remain in the bloc, as did Scotland.

Unionists in Northern Ireland have been irked by the agreement, saying it drives a wedge between the province and the rest of the mainland UK.

In the meantime, London has complained that the protocol creates unnecessary red tape.

The EU Commission last October proposed cutting bureaucratic hurdles, but the UK has rejected those plans, and said it would introduce legislation to suspend parts of the protocol.

Johnson plans to introduce the legislation on Thursday. He survived a vote of no-confidence from his own Conservative MPs on Monday.

Practical problems, political will

Martin argued to MEPs that with good will from London, solutions could be found.

"I have said many times that there are solutions to practical problems under the protocol if there is a political will to find them," he said.

EU officials and US politicians have also warned the Johnson government that unilateral moves could destabilise the region.

"It would mark a historic low-point signalling a disregard for essential principles of laws which are the foundation of international relations," Martin said, adding that it would "be to the benefit of absolutely no one".

The UK's former Brexit negotiator David Frost has recently blamed the EU's rigidity and Ireland's insistence on keeping the "all-island economy" intact for the failure of the protocol.

The argument on the "all-island economy" — avoiding a hard border on the island of Ireland — "suited the political needs of the EU and Ireland", Frost argued in the foreword of a recent report.

Only four percent of the goods and services produced in Northern Ireland cross the border to the Republic, while 16 percent go to Great Britain, and 31 percent of imports to Northern Ireland are from the rest of the UK, the report said.

Nevertheless, consecutive Tory governments in London argued for a type of Brexit that meant also exiting the EU's customs union.

EU officials have argued that the particular type of Brexit created the need for the protocol, as a way to handle trade between Northern Ireland and the republic of Ireland.