Taoiseach Leo Varadkar has said it would not be undemocratic to hold a second Brexit referendum.
After addressing the European Parliament in Strasbourg, Mr Varadkar was challenged by former Ukip leader Nigel Farage who accused him of trying to overturn the UK’s split from Europe.
The Taoiseach declined to say whether the referendum should be re-run and denied being part of a secret plot to reverse the vote.
"I don’t think it would be constructive or helpful for the leader of another country to be advising that other country whether they should or should not have a second vote," he said.
Mr Varadkar said referendums had been re-run in Ireland - including the contentious second vote on the Lisbon Treaty which helped pave the way for a bigger EU - but he said Ireland made those decisions alone.
And he added: "I don’t think it’s anti-democratic for people to change their minds or have a second vote but any decision on the second referendum must only be one for the UK parliament and the UK people.
"We shouldn’t tell them to do that or put any pressure or expectation on them in any way. I think that would be counter-productive."
The Taoiseach also denied being part of a conspiracy with the likes of former British prime minister Tony Blair and deputy prime minister Nick Clegg to thwart Brexit.
"I’m certainly not party to any plot against the United Kingdom. I’m a friend of the United Kingdom and certainly want to be a friend of the United Kingdom," he said.
Mr Farage told the Taoiseach: "You don’t want Britain to leave because you know if you do others will leave too.
"And I would just say this to you. I don’t want a second referendum on Brexit. Absolutely not but I fear that you are all working together with Tony Blair and Nick Clegg to make sure we get the worst possible deal.
"I say that because I have seen it all before. The difference is if you force the Brits to do it again it will be a different outcome."
Mr Farage branded the Taoiseach a European unionist.
Earlier Jean Claude Juncker has said he would be happy to help Britain rejoin the European Union if it wants to after Brexit.
The European Commission president said the UK could apply to rejoin under Article 49 of the Lisbon Treaty even after it leaves the EU in March 2019 - if the Government or British people want to "find a way out" of Brexit.
It comes after European Council president Donald Tusk said on Tuesday he was open to a "change of heart" from the UK.
Mr Juncker described Brexit as a "lose-lose situation" for Britain and the EU and a "catastrophe".
And addressing the European Parliament in Strasbourg on Wednesday, he went on: "Mr Tusk said that our hand remains outstretched.
"The British people, the British Government, may wish to find a different way out of the Brexit situation and we are very much willing to deal with them."