Brexit tensions between Britain and the European Union exploded into an open war of words today, with both sides accusing the other of sowing disharmony at the Group of Seven summit.
Ever since the UK voted to leave the EU in 2016, the two sides have been trying to solve post-Brexit trading arrangements in Northern Ireland.
The latest spat is centred on sausages. During talks with Emmanuel Macron at the G7 summit in England, British Prime Minister Boris Johnson had queried how the French president would react if Toulouse sausages could not be sold in Paris markets.
Britain's Telegraph newspaper reported that Mr Macron responded by saying Northern Ireland was not part of the United Kingdom, remarks British foreign minister Dominic Raab described as "offensive".
"Various EU figures here in Carbis Bay, but frankly for months now and years, have characterised Northern Ireland as somehow a separate country and that is wrong," Mr Raab said.
"It is a failure to understand the facts. We wouldn't talk about Catalonia and Barcelona, or Corsica in France in those ways," he told the BBC's Andrew Marr programme.
The British Prime Minister has threatened to use emergency measures in the Northern Ireland Protocol of the Brexit divorce deal if no solution is found.
The protocol essentially keeps Northern Ireland in the EU's customs union and adhering to many of the single market rules, creating a regulatory border in the Irish Sea between Northern Ireland and the rest of the UK.
But Mr Johnson has already delayed the implementation of some provisions of the protocol, including checks on chilled meats such as sausages moving from Britain to Northern Ireland, saying it was causing disruption to some NI supplies.
A French diplomatic source said Mr Macron had been taken aback by Mr Johnson bringing up sausages - which the British leader had said was a crucial issue but the French regarded as a distraction from the main G7 business.
The French president had merely been pointing out the sausage comparison was invalid due to the geographic differences, the source said.
"It took four years to negotiate this deal," the source said. "It cannot be said the United Kingdom didn't know what it was signing for. It's either not very professional or a distraction from the real issues."
Repeatedly questioned at a media conference about Mr Macron's comments during their talks, Mr Johnson said Brexit had occupied a "vanishingly small proportion of our deliberations" during the G7 summit which ended today.
"We will do whatever it takes to protect the territorial integrity of the UK but actually what happened at this summit was that there was a colossal amount of work on subjects that had absolutely nothing to do with Brexit," he said.
President Macron said that France respects Britain's sovereignty but it is time to end rows over sausages and focus on more serious issues.
"My wish is that we succeed collectively in putting into action what we signed several months ago," Mr Macron told a news conference at the G7 leaders' summit.
"Let's not waste time with controversies that are created in corridors and backrooms."
DUP sends Good Friday Agreement to France
Meanwhile, DUP Leader Edwin Poots said he has sent Mr Macron a copy of the Good Friday Agreement.
Mr Poots said: "Emmanuel Macron's suggestion that Northern Ireland is not part of the United Kingdom is offensive and demands a statement from the French administration which recognises Northern Ireland's constitutional status.
"This also exposes the ignorance which lies at the heart of the EU. They seem blind to the destruction the protocol has caused to the Belfast Agreement.
"It's five years since the (Brexit) referendum. Northern Ireland has been centre stage for most of that time yet the most powerful man in one of the most powerful EU countries still doesn't realise that Northern Ireland is part of the United Kingdom. It's incredible."
The DUP leader added: "Key leaders in the European Union clearly do not even understand the basics let alone the finer details.
"It is time for the government to stop talking about fixes to the protocol and get on with taking the necessary steps to remove it."
'Very problematic' if UK again extends grace period
Earlier, speaking on the Trevor Phillips on Sunday programme on Sky News, Taoiseach Micheál Martin said it will be "very problematic" if the UK again extends unilaterally the grace period for Northern Ireland Protocol checks.
However, Mr Martin also insisted a breakthrough between the EU and UK was still possible "if there's a will there on both sides".
His comments came after Mr Johnson yesterday escalated his dispute with the European Union by warning he will do whatever it takes to keep goods flowing from Britain to Northern Ireland.
Following talks with the EU's key figures, Mr Johnson said he would not hesitate to take unilateral action to protect the position of Northern Ireland in the increasingly bitter row over post-Brexit trading arrangements.
The row could mean chilled meats will not be shipped across the Irish Sea because of EU rules after the end of the month.
The UK is considering extending the current grace period without the consent of Brussels to ensure that sausages and mince can continue to reach Northern Ireland's shops.
But Mr Martin told Sky News that the "channels do exist to get this resolved".
He added: "In particular, the Šefcovic/Frost process should be fully explored and optimised to get an agreement and I think the prospects, in my view, if there's a will there on both sides, and there is a will there from the European Union side I know that, I detect from the British Prime Minister Boris Johnson that the British government is anxious to get a resolution of this, so I think we should work at it."
Mr Martin said he believed an SPS agreement (on plant and animal health measures) could remove 80% of protocol checks.
When asked about the possibility of the UK unilaterally extending the grace period for checks, Mr Martin said: "I think it will be very problematic because it is not about sausages per se, it really is about the fact that an agreement had been entered into, not too long ago, signed off by the British government with the European Union.
"If there's consistent, unilateral deviation from that agreement, that clearly undermines the broader relationship between the European Union and the United Kingdom, which is in nobody's interest and therefore that's why the UK with the EU have to work very hard now in the coming weeks.
"I know the European Union are anxious to resolve this and want to resolve it but they need to see a similar reciprocity from the UK side."
When asked if the protocol is undermining Northern Ireland's place within the UK, Mr Martin said: "We've never seen the protocol as a constitutional issue, it doesn't in any way interfere with the constitutional status of Northern Ireland as defined and articulated in the Good Friday Agreement.
"We're very clear from the Irish Government perspective on that, but we do believe in seamless trade on the island of Ireland, it makes sense. We believe in seamless trade in so far as we possibly can between the United Kingdom and Northern Ireland."
Minister for Foreign Affairs Simon Coveney said that after the G7 summit, Mr Johnson will be in no doubt as to the strength of feeling within the EU and from Washington as to concern around non-implementation of the Northern Ireland protocol.
Speaking to RTÉ's This Week, Mr Coveney said he believes that Mr Johnson knows that if the UK breaches the protocol or acts unilaterally again without permission from the EU, there will be consequences.
He said Ireland wants to solve the problems but it and the EU need partnership on the UK side.
Mr Coveney said experienced negotiators are needed on both sides to honour the commitments.
He said there are proposals coming from the EU and UK sides currently.
Mr Coveney said he met with the UK’s chief Brexit minister David Frost a week ago to talk through the issues.
He added people need to be honest with businesses in Northern Ireland about what the protocol is as he said it has not been explained in terms of its consequences.
Some people, he said, think the protocol can be replaced.
Mr Coveney said it is very helpful that the US reassured the UK in relation to common standard towards food safety and animal health.
He said the EU is looking at progressing solutions to other problems, such as the consistency of medicines from Britain to Northern Ireland uninterrupted.