Micheál Martin has welcomed the European Commission's decision not to invoke Article 16 of the Northern Ireland protocol on Brexit.
In an extraordinary move that blindsided both the UK and Ireland, the EU invoked Article 16 of the Northern Ireland Protocol to stop the unimpeded flow of vaccines from the bloc into the region.
Late on Friday night, Brussels U-turned on the move, following condemnation from Dublin ,Belfast and London.
British prime minister Boris Johnson spoke with European Commissioner Ursula von der Leyen to express his "grave concern" at the development.
Taoiseach Micheál Martin held multiple phone calls with Ms von der Leyen on Friday night in a bid to resolve the issue.
He tweeted: "Welcome decision by the European Commission tonight not to invoke the safeguard clause of the Ireland / Northern Ireland Protocol following constructive discussions with @vonderleyen
The move was universally condemned by politicians in Dublin, Belfast and London, forcing an embarrassing U-turn from the European Commission, which claimed the incident had been an "oversight."
In a statement late on Friday, the Commission said it is "not triggering the safeguard clause" to ensure the Northern Ireland Protocol is "unaffected" after widespread condemnation of its move as part of its export controls on coronavirus vaccines.
The statement read: "To tackle the current lack of transparency of vaccine exports outside the EU, the Commission is putting in place a measure requiring that such exports are subject to authorisation by Member States.
"Should transits of vaccines and active substances toward third countries to be abused to circumvent the effects of the authorisation system, the EU will consider all using all the instruments at its disposal."
Responding, Foreign Affairs Minister Simon Coveney tweeted: "Welcome news, but lessons should be learned; the Protocol is not something to be tampered with lightly, it's an essential, hard won compromise, protecting peace & trade for many."
Former DUP MP, Lord Nigel Dodds slammed the EU for what he called a "hostile act", which "exposes the entire hypocrisy of the Northern Ireland Protocol".
He told BBC Newsnight: "I'm not surprised the EU is scrambling around having made a complete mess of the situation throughout this week.
"What the EU did, in implementing Article 16 and overriding parts of the protocol, this whole approach to Northern Ireland has been based on a hypocrisy and a falsehood over a number of years.
"They were prepared, and they still are, to reserve the position that they will in the future if necessary, invoke Article 16 in order to create a hard border in the island of Ireland, for vaccines to help people get through a pandemic.
"It's outrageous. It is a hostile act, as the DUP leader has said, and it exposes the entire hypocrisy of the Northern Ireland Protocol."
A chaotic Friday night saw diplomatic channels lighting up between London and Brussels in a bid to resolve the issue.
Neither the UK PM or the Taoiseach was informed of Brussels' intention to invoke Article 16 of the protocol ahead of time, the PA news agency understands.
The protocol, which is part of the Withdrawal Agreement, is designed to allow the free movement of goods from the EU into Northern Ireland, and prevent the need for a hard border on the island of Ireland.