Mr Frost is expected to use his speech to the diplomatic community in the Portuguese capital, Lisbon, on Tuesday to set out concerns over the Northern Ireland Protocol, stressing the need for "significant change" in order to restore genuinely good relations between London and Brussels. However, Mr Coveney, a close ally of former Taoiseach Leo Varadkar, was quick to outline his concerns on social media.

       He posted: “EU working seriously to resolve practical issues with implementation of Protocol - so UKG creates a new “red line” barrier to progress, that they know EU can’t move on…. are we surprised?

       “Real Q: Does UKG actually want an agreed way forward or a further breakdown in relations?”

       Lord Frost was quick to reply, responding: “I prefer not to do negotiations by twitter, but since @simoncoveney has begun the process...the issue of governance & the CJEU is not new.

       “We set out our concerns three months ago in our 21 July Command Paper.

       “The problem is that too few people seem to have listened.”

       He added: “We await proposals from @MarosSefcovic. We will look at them seriously & positively whatever they say. We will discuss them seriously and intensively.

       “But there needs to be significant change to the current situation if there is to be a positive outcome.”

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       Replying to Mr Frost's tweet, Brenda Spiller said: "Trigger article 16, you'll get their attention then. It's important to follow through on 'promises'.

       "I'd prefer you just ditch the whole WA & not pay the EU a sou, but that's just me.

       "Should have always been a clean break from these technocrats."

       Sam Thompson said: "The protocol must go, it benefits no-one, neither business or public."

       However, others questioned why the UK had signed the deal in the first place, given Lord Frost's remarks.

       Adrian Fitzpatrick said: "UK government signs a deal, wins election based on the fact it has a great deal, now wants to renege on deal telling the other side it's being unreasonable."

       Mike Chamberlain commented: "Have you recently signed a legally binding international agreement after zero scrutiny with a clause you don’t like?

       "Then call our legal team at Tough **** You Signed It. Our legal team will laugh down the phone at you for a large fee payable in advance.

       During his speech, Lord Frost is expected to say endless negotiation is not an option and that London will need to act using the Article 16 safeguard mechanism if solutions cannot be agreed rapidly, according to extracts of his speech released by his office on Saturday.

       Article 16 allows either side to take unilateral action if the protocol is deemed to have a negative impact.

       The transcript reads: "No one should be in any doubt about the seriousness of the situation.

       "The EU now needs to show ambition and willingness to tackle the fundamental issues at the heart of the Protocol head on.

       "The UK-EU relationship is under strain, but it doesn't have to be this way.

       "By putting the Protocol on a durable footing, we have the opportunity to move past the difficulties of the past year."

       Frost is also expected to signal a desire to free the protocol from the oversight of European judges.

       "The role of the European Court of Justice (ECJ) in Northern Ireland and the consequent inability of the UK government to implement the very sensitive arrangements in the Protocol in a reasonable way has created a deep imbalance in the way the Protocol operates."