Tánaiste and Minister for Foreign Affairs Simon Coveney has ruled-out any renegotiation of the Withdrawal Agreement, which maps-out Britain's exit from the European Union, if Theresa May is replaced as British Prime Minister.
Speaking on RTÉ's This Week, Mr Coveney said: "It's not up for renegotiation, even if there is a new British prime minister...the personality might change here, but the facts don't."
He described Mrs May as "a decent person" but strongly criticised Conservative MPs at Westminster - branding them as "impossible" on the issue of Brexit.
In some of his strongest comments to date, Mr Coveney said: "There are many British politicians who don't, quite frankly, understand the complexity of politics in Northern Ireland."
The Tánaiste added: "They have tried to dumb this debate down into a simplistic argument whereby it's Britain versus the EU, as opposed to two friends tying to navigate through the complexity of a very, very difficult agreement."
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Mr Coveney also said the Government will continue to focus significant efforts and financial resources towards planning for a no-deal Brexit scenario, following Friday's collapse of Brexit talks in the UK.
He said time was of the essence for the UK to get a deal through parliament, adding he was concerned that Britain would not get its act together over summer, and leave without a deal.
Mr Coveney said the EU has always been open to changing the Future Relationship Declaration but not the Withdrawal Agreement and if that involved a shared customs union, the EU is up for that if it could get a majority in Westminster.
"The danger of course, is that the British system will simply not be able to deal with this issue and even though there's a majority in Westminster that want to avoid a no-deal Brexit, and that is why over the summer months we will continue to focus significant efforts and financial resources on contingency planning to prepare for that worst case scenario."
He said he has not taken his eye off Brexit for one second, even though an extension has been granted until October and until we get certainty from Westminster, we have to continue no-deal Brexit planning.
The Tánaiste said there was a very real effort to try in the UK to find compromise but it had failed on some key issues.
He said it was extraordinary how opposition parties in the UK could not support each other during such times, when in Ireland, opposition parties have supported the Government to get things through.
He said the more Mrs May tries to bring in opposition parties, the more she loses her own people.
Mr Coveney said he thought Mrs May's focus is now more on trying to protect her country and bringing her country together, as Britain has become seriously divided on the Brexit question.