Simon Coveney said Boris Johnson’s approach – demanding the abolition of the Irish backstop or else Britain will leave without a deal – is “making a no-deal far more likely”.
Speaking ahead of Mr Johnson’s Europe trip this week, Mr Coveney said: “There is a reason why Boris Johnson is visiting Berlin today and Paris tomorrow, to try to talk to EU leaders about finding a way forward.
“I think he will get a very consistent message from EU leaders that the negotiations over the last two to three years are not going to be abandoned now.”
But Mr Coveney, who is also Ireland’s foreign affairs minister, held out some hope that the impasse could still be broken.
He said: “We will try and find a way to give the reassurance and clarification that Boris Johnson needs to sell a deal.
“We will try and be imaginative about that and be helpful on that.”
Mr Johnson will hold talks with German Chancellor Angela Merkel later on Wednesday, followed by discussions with French President Emmanuel Macron on Thursday.
He is expected to repeat his demand that the EU scraps the backstop, an insurance policy designed to avoid the return of a hard border on the island of Ireland.
Speaking ahead of their meeting, Ms Merkel said she would discuss with the PM how to make Britain’s exit from the EU as smooth as possible.
“Today I will talk with the British prime minister, who is visiting me, about how we can get the most friction-free British exit from the European Union possible as we must fight for our economic growth,” she said.
Since taking office last month, Mr Johnson has said the arrangement is the major stumbling block to getting a deal passed by MPs.
The deadlock over the backstop is seen as increasing the chances of a no-deal Brexit at the end of October, something the PM has not ruled out pursuing.
In a letter to Donald Tusk, seen as the opening gambit in his bid to secure changes to the deal negotiated by Theresa May, Mr Johnson set out his opposition to the “anti-democratic” measure.
The PM said he would be willing to give Brussels the “commitments” it needs that alternatives to the backstop can be put into effect.
But the European Council president gave the demand short shrift, writing on Twitter: “The backstop is an insurance to avoid a hard border on the island of Ireland unless and until an alternative is found.
“Those against the backstop and not proposing realistic alternatives in fact support re-establishing a border. Even if they do not admit it.”
The pair will hold talks on Sunday during the G7 summit in the French city of Biarritz.
Brussels has consistently rejected calls to scrap the backstop and reiterated that the deal agreed with Mrs May is not up for renegotiation.
The backstop would come into effect if the Irish border issue could not be sorted out during negotiations between the two sides on a future trade deal.
The UK as a whole would remain in a customs union with the EU, while Northern Ireland would follow further EU rules and regulations in order to keep the border with Ireland – an EU member – frictionless.
But it is opposed by many Conservative MPs and Northern Ireland’s Democratic Unionist Party, which supports the Tories in key Commons votes.
They oppose it because they fear it will weaken the constitutional integrity of the Union – as Northern Ireland would be treated differently to the rest of the UK by following different rules and regulations.
Opponents have also expressed fears Britain could end up being trapped in the arrangement – and by extension the EU.
Mr Coveney, however, said the backstop had to stay.
“We are not going to abandon a solution that we know works for some kind of promise on the basis of trust that we will all work together to try and find a solution and muddle on in the future to solve the border,” he told RTE Radio One.
“If we do that, what we will be doing is we will be creating collateral damage in Ireland to solve a problem in Westminster and for the next number of years, the border issue will dominate Irish politics, north and south because we haven’t resolved it in the way we that know we can.”