Taoiseach Leo Varadkar has lashed out at British foreign secretary Boris Johnson over his failure to understand the Irish stand-off, .
The Taoiseach said Mr Johnson's views are "just not the case" and that it would be "absolutely beneficial" for him to visit the border.
Speaking to reporters after Mr Johnson was heard on a leaked recording of a private function on Thursday evening claiming the border issue is a minor matter and should not be the tail wagging the dog of British negotiators, Mr Varadkar said Mr Johnson could do with visiting the border to inform himself of the facts.
"I just don't think it's [Mr Johnson's comments] accurate, the fact he's described the border that exists as being like a border between two London boroughs, it's something that's just not the case.
"I think it would be absolutely beneficial for anybody involved in talks on Brexit to visit the border. David Davis has done that and I know a lot of European leaders have done that too.
But as I say, when it comes to wanting to know and understand what the British government's position is I speak to Theresa May," Mr Varadkar said.
British Prime Minister Theresa May still has full confidence in Boris Johnson, Downing Street has said.
A No. 10 spokeswoman refused to comment on the leaked recording of the British Foreign Secretary's indiscreet assessment of Brexit.
Former Tory leader Lord Howard has said British Foreign Secretary Boris Johnson's warning of a Brexit "meltdown" was part of the "spills and thrills" of EU withdrawal negotiations.
He told BBC Radio 4's Today programme: "There were always going to be spills and thrills during the negotiation."
Asked about Mr Johnson's claim that officials in the British Treasury were working against the long-term gains of Brexit, Lord Howard said: "If there are people in the Treasury who are doing that then they shouldn't be doing that, and I deplore that."
He's certainly right to say we shouldn't panic. I don't know about a meltdown. I'm not as close to the negotiations as Boris is. - Lord Howard
"What we have to do is to focus on the essentials of the situation. The essentials are that the European Union wants a deal and there is every prospect therefore that if we hold our nerve that we could get a good deal, a good deal for them and a good deal for us, because it is in our mutual interests that that should happen."
Senior Conservative Sarah Wollaston suggested Mr Johnson knew the comments would be leaked.
She said: "Boris 'leak' a bit like him using the Tory WhatsApp group as a kind of deniable press briefing.
"Dressing up publicly broadcast insults under the cover of a 'private' discussions won't wash."
Theresa May was under fresh pressure from within the Cabinet after Boris Johnson warned of a Brexit “meltdown” and called for “guts” in exit talks.
In unguarded comments at a private dinner, the British Foreign Secretary said there was a risk Brexit “will not be the one we want” and would keep the UK “locked in orbit” around the EU.
At the gathering of the Conservative Way Forward, a Thatcherite campaign group, he branded the Treasury the “heart of Remain” and claimed negotiations were approaching a “moment of truth”.
In comments captured in a recording obtained by BuzzFeed News, he said the British Prime Minister was “going to go into a phase where we are much more combative with Brussels”.
He added: “You’ve got to face the fact there may now be a meltdown. OK? I don’t want anybody to panic during the meltdown. No panic. Pro bono publico, no bloody panic. It’s going to be alright in the end.”
Mr Johnson suggested Chancellor Philip Hammond’s department was “basically the heart of Remain” and said the UK could end up “in the customs union and to a large extent still in the single market”.
The Cabinet minister was speaking to around 20 people dining in a private room after a reception at the Institute of Directors on Wednesday night.
He said: “Unless you make the change, unless you have the guts to go for the independent policy, you’re never going to get the economic benefits of Brexit. You’ll never get the political benefits of Brexit.”
Mr Johnson said fears about the border on the island of Ireland were out of proportion.
“It’s so small and there are so few firms that actually use that border regularly, it’s just beyond belief that we’re allowing the tail to wag the dog in this way,” he added.
“We’re allowing the whole of our agenda to be dictated by this folly.”
Mr Johnson also suggested Donald Trump would “go in bloody hard” and “might get somewhere” in the exit talks if he was in charge.
The US president, meanwhile, has grown tired of Mrs May’s “school mistress” tone, his allies have told the Daily Telegraph.
His comments are the latest Brexit headache for the British Prime Minister, who is in Canada for the G7 summit.
The Foreign Secretary’s deputy, Alan Duncan, raised eyebrows in Westminster when he floated the possibility of a referendum on the exit deal.
Mrs May also met twice with David Davis before flying out to the summit amid reports the Brexit Secretary was considering resigning unless she set a clear time limit on the temporary customs arrangement.
Friends of Mr Johnson said: “This was a private dinner under Chatham House rules so it is sad and very disappointing that it has been covertly recorded and distributed to the media.”
Michel Barnier, the EU’s chief Brexit negotiator, is expected to hold a press conference in Brussels at around 1pm to discuss the latest round of technical talks on the exit process.
Mrs May secured approval from senior ministers for a “backstop” arrangement that could keep the UK in a customs union with the EU beyond the end of 2020.
But there was no fixed deadline in the document published later, which said only the UK “expects” a final customs solution to be in place by the end of December 2021 at the latest.
The document represents the UK’s counter to an EU proposal to keep Northern Ireland alone in the customs union after Brexit, which was rejected outright by Mrs May because it would draw a border down the Irish Sea.
In a letter to Tory MPs, obtained by The Times, the British Prime Minister described the UK proposal as “unpalatable but at worst temporary” and “in no way the Government’s intended or desired” result.
At the same time the UK would be able to strike free trade agreements with other countries.
Mrs May braced herself for possible defeat in the Commons next week on an amendment which would require her to try to negotiate a permanent customs union with the remaining EU.
The British PM has rejected most of the amendments made to the EU (Withdrawal) Bill made by peers, accepting only one in full.