Boris Johnson on Saturday issued a defiant warning that he would not hesitate to suspend parts of his Brexit deal on Northern Ireland unless the EU stopped dealing with the issue in a “theologically draconian” way.

The British prime minister came out swinging after a series of meetings with EU leaders in the margins of the G7 summit in Cornwall, claiming that some of them did not understand the Northern Ireland problem.

Rather than calming the rhetoric, as requested by US president Joe Biden, Johnson struck a robust tone in a series of broadcast interviews, insisting he would do “whatever it takes” to defend the UK’s territorial integrity.

Johnson was accompanied in a meeting with EU leaders by David Frost, Brexit minister, who wore union jack socks. Dominic Raab, foreign secretary, accused the EU of being “bloody minded”.

Earlier Emmanuel Macron, French president, urged Johnson to keep his word and honour his Brexit commitments. An Elysée source said that this was important if efforts to “reset” UK/France relations were to succeed.

But Johnson told broadcasters that he was willing to unilaterally activate Article 16 — the override mechanism that suspends parts of the Northern Ireland protocol.

The protocol provides for an open border in Ireland, but creates new checks on goods travelling from Great Britain to NI to avoid them passing through the region and into the EU single market.

Johnson claims the EU wants the checks on trade between two constituent parts of the UK to be applied in a “draconian” way, including a ban from July 1 on trade in chilled meats.

“If the protocol continues to be applied in this way, then we will obviously not hesitate to invoke Article 16,” he said. Talks will continue between London and Brussels in the coming days.

Johnson added: “I’ve talked to some of our friends here today, who do seem to misunderstand that the UK is a single country, a single territory. I just need to get that into their heads.

“I think that what our friends have also understood is that it’s the prime duty of the UK government to uphold the territorial integrity of the United Kingdom.”

Both the EU and UK are entitled to invoke Article 16 in the event of the Northern Ireland protocol causing “economic, societal or environmental difficulties”.

The EU has threatened to punish Britain — including imposing trade sanctions — if Johnson unilaterally breaks commitments on border checks made in the Northern Ireland protocol, part of his Brexit deal.

At a breakfast meeting on the margins of the G7 summit in Cornwall, Macron made it clear he expected Johnson to honour the Brexit deal sealed with the EU last December.

An Elysée source said: “The president strongly underlined that this re-engagement requires the British to honour the promises made to Europeans and to respect the Brexit agreement.”

A clash is approaching later this month on exports of chilled meat products across the Irish Sea; the EU only permits trade in frozen meat. A “grace period” to allow continued sale of British sausages, minced beef and chicken nuggets in Northern Ireland expires at the end of June.

Maros Sefcovic, European Commission vice-president, confirmed last week that if the UK unilaterally suspended the protocol then Brussels’ response could include trade sanctions, spawning fears of a trade war or — in tabloid headlines — a “sausage war”.

Johnson also held talks on Saturday morning with Angela Merkel, German chancellor, and European Council president Charles Michel and European Commission president Ursula von der Leyen.

Von der Leyen said in a tweet that the Good Friday Agreement and peace on the island of Ireland were paramount.

“We negotiated a protocol that preserves this, signed and ratified by the UK and EU,” she said. “We want the best possible relations with the UK. Both sides must implement what we agreed on. There is complete EU unity on this.”