The EU will not renegotiate the Brexit withdrawal deal regardless of who the UK’s next prime minister is, Ireland’s foreign minister has warned.

Simon Coveney described political events at Westminster as “extraordinary”, as he questioned the logic of politicians who believed a change of leader would deliver changes to the agreement struck by Theresa May.

“The EU has said very clearly that the Withdrawal Agreement has been negotiated over two-and-a-half years, it was agreed with the British government and the British cabinet and it’s not up for renegotiation, even if there is a new British prime minister,” he said.

“The personality might change but the facts don’t.”

In a scathing assessment of the political situation in the UK, Mr Coveney told RTE that Britain could trigger a no deal by “default” if its MPs failed to get their act together.

He said he believed Mrs May was a “decent person” trying to find a middle ground position, but had been thwarted by an “impossible” Conservative Party.

Mr Coveney said the UK should not assume another extension will be granted by the EU if a deal is not agreed by the latest October deadline. He said the EU was set for major changes and challenges as a result of the European elections and would likely be prepared to devote less focus on Brexit going forward.

“That’s my concern – that Britain will fail to get its act together over the summer,” he said.

“There will be people like Nigel Farage and some within the Conservative Party who will be making the proposition that ‘look, we have had enough of this, let’s just leave on WTO (World Trade Organisation) terms without a deal’ – in my view not fully understanding or not being honest about the full consequences of that for Britain and Ireland.”

He added: “The danger of course is that the British system will simply not be able to deal with this issue and even though there is a majority in Westminster who want to be able to prevent a no-deal Brexit it could happen by default.”

Mr Coveney said Ireland would continue its no-deal Brexit contingency planning .

He noted that political parties had largely spoken with the same voice in Ireland.

“In the UK no two parties seem to be able to agree on anything, despite the extraordinary dangers that Britain is potentially going to be exposed to in the autumn,” he said.

Noting the prospect of Mrs May offering pledges on technological solutions for the Irish border in her final bid to get the withdrawal treaty through Parliament next month, Mr Coveney said he did not have an issue with that as long as it did not undermine the border backstop provisions within the Withdrawal Agreement.

The Tanaiste said UK politicians who thought a new prime minister could strike a new deal did not understand the EU.

“For the EU and Ireland this has always been about the complexity of Brexit, trying to protect the EU, its integrity, its single market, its customs union, its members and also trying to respect the decision of British people,” he said.

“It’s always been about that. For Britain in many ways it’s been about party politics and personalities and many people seem to think that Britain would have got a much better deal if only they had a tougher prime minister.

“In my view that just is a fundamental misunderstanding of how the European Union operates.

“The EU is a treaty-based, precedent-based series of institutions, it doesn’t have a lot of flexibility and that’s why this negotiation has been about detail, regulation, legal provisions and so on.

“And I think the British Prime Minister understands that and that is why she has agreed to reasonable compromises in certain areas.

“But there are many British politicians who don’t, quite frankly, understand that or the complexity of politics in Northern Ireland and therefore 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.”