Tensions over Brexit threatened to overshadow the final day of the G7 Summit.London accused France on Sunday of offensive remarks that Northern Ireland was not part of the UK.The conflict relates to the Northern Ireland protocol in the Brexit deal signed by Prime Minister Boris Johnson.That protocol essentially kept the province in the EU's customs union to avoid a hard border between Ireland and Northern Ireland.But it also meant the need for trade checks across the Irish Sea to protect the integrity of the EU's single market.Something the UK government has resisted implementing.At his closing news conference, Johnson attempted to play down the row but reasserted his position."What I'm saying is that 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."During tense talks on Saturday, Johnson asked French President Emmanual Macron how he would feel if Toulouse sausage makers could not sell their products in Paris markets, echoing London's accusation that the EU is preventing sales of British chilled meats in Northern Ireland.British media reported that Macron responded by inaccurately saying Northern Ireland was not part of the United Kingdom.Later, Macron said he respected British sovereignty but that trade rules had to be honored.He called on the UK to implement what was collectively agreed months ago:"What I have to say to Prime Minister Boris Johnson, I tell him and I tell you now: France has never allowed itself to question British sovereignty, the British territorial integrity and the respect of that sovereignty."Northern Ireland remains deeply split along sectarian lines.Many Catholic nationalists aspire to unification with Ireland while Protestant unionists want to stay in the UK.Unionists have been angered by the protocol which they say cuts them off from the rest of Britain.That anger spilled out into the streets in April, when Belfast saw some of its worst violence in years.