Enda Kenny reiterated calls for the United Kingdom to remain in the European Union during what is understood to have been a frank exchange of views during Friday's British Irish Council meeting, in Glasgow.
Although official Leave and Remain campaigns are both suspended in the wake of Thursday's killing of Labour MP Jo Cox, the Taoiseach took the opportunity to warn that Britain's role would be diminished outside the EU and once more called upon the Irish in the UK to vote to stay.
One well-placed source said that Mr Kenny "really went for it" during the meeting between representatives from the UK, Irish, Scottish, Welsh, Northern Irish governments, as well as delegates from the Isle of Man, Jersey, and Guernsey.
“Kenny was crystal clear. He was very focused in what he wanted to impart to the meeting. He got broad support from others around the table,” said another source.
The council meeting discussed a range of subjects including support for carers and closing the attainment gap, but the possibility of Brexit took centre stage.
Flanked by Scottish first minister Nicola Sturgeon and Martin McGuinness at a press conference after the meeting, the Taoiseach spoke about the "closeness of relations, socially, economically and politically" between Britain and Ireland and warned that it would be a "massive change" if the UK left the EU.
“I have the privilege to sit around the table at the European Council and Britain has always been a strong sensible voice there we would like that to continue,” he said.
If Britain voted to leave "there would not be any representative there to speak for Scotland, England, Wales or Northern Ireland" at the European Council. The Taoiseach's concerns were shared by Allan Bell, chief minister in the Isle of Man government.
Mr Kenny repeated calls for the Irish in the UK to vote to remain. “We feel it is important to speak to the Irish community who are entitled to vote in the referendum and to say to them unashamedly that we believe very strongly that they should vote to stay in as a member of the European Union,” he said.
Ms Sturgeon, who is also campaigning for a Remain vote, said that regardless of the result on Thursday “the very strong relationship between the Scottish government and the Irish Government will continue”. The Scottish first minister cited a recently opened investment hub in Dublin and the visit of President Michael D Higgins to Scotland later this month.
Mr Kenny paid tribute to Ms Cox and sent his condolences to her husband, Brendan, and the couple’s two children.
Ms Cox’s killing “hit all of us as politicians very hard”, said Ms Sturgeon. “But I think I speak on behalf of all of us when I say we are determined, and inspired by Jo Cox, to rededicate ourselves to the notion of politics and public service as a force for good,” the Scottish first minister added.
Mr McGuinness said that both he and his opposite number, DUP first minister Arlene Foster, who was also in attendance, had firsthand experience of threats. "I have been threatened many times over my role in the peace process by people who don't agree with the peace process and are still committed to violence," the Stormont deputy first minister said.
“Under no circumstances would I ever countenance changing my routine to satisfy those who want to take us back to conflict.”
Northern Ireland Secretary of State Theresa Villiers declined to comment on the specifics of the discussion inside the British Irish Council meeting but dismissed concerns that a vote to leave the EU would damage relations between Ireland and the UK. Warnings from Mr Kenny, British prime minister David Cameron and others that a Brexit vote could see the return of Border controls were "a scare story", she added.
“The Common Travel Area survived a civil war, a world war and 30 years of the Troubles. There is every reason to believe it will survive a Brexit vote. I believe It will.”