Jones asks if DUP MPs run UK, after Brexit talks failure
Wales' First Minister Carwyn Jones has asked whether the UK is being run by "ten MPs from Northern Ireland".
Theresa May failed to reach agreement with the EU after a DUP backlash against proposals for the Irish border.
Mr Jones said no part of the UK can "be more favourably treated than others", after reports the UK hoped to announce an unique Northern Ireland Brexit deal.
Earlier, Brexit Secretary David Davis accused Mr Jones and others of spreading "falsehoods" on the matter.
Mr Davis told MPs UK ministers were "emphatically" not considering "the suggestion that we may depart the European Union but leave one part of the UK behind still inside the single market and customs union".
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Northern Ireland's Democratic Unionist Party (DUP) has a deal with Theresa May's minority government in Westminster to help the Conservatives survive key Commons votes.
The DUP scuppered a deal between the UK and the EU on Monday on the first phase of the negotiations that would have seen "regulatory alignment" between Northern Ireland and the Republic of Ireland - intended to avoid the need for border checks after Brexit.
Concern was raised by Welsh politicians that it could lead to the Irish Sea becoming a border between the UK and the island of Ireland, leading to a knock-on effect on Welsh ports.
Responding to an emergency question in the assembly on Tuesday, the first minister said the Irish government shared the concerns of ministers in Cardiff.
"The last thing they want to see is a hard border between Wales and Ireland as a maritime border," he said.
"The UK government has a responsibility to secure a deal that is good for the whole of the UK."
"It is quite clear yesterday that they were looking to arrange a special deal or special status for Northern Ireland," Carwyn Jones added.
Mr Jones said the DUP had "torpedoed" the deal UK ministers had been aiming to secure in Brussels "which asks the question why it is a small party in Northern Ireland has the ability to have a veto over what is good for the UK in terms of the negotiations with the EU".
"Really the question is this, is the prime minister really in charge of the UK or is the UK in the charge of 10 MPs from Northern Ireland?"
Meanwhile, at Westminster, Mr Davis said he wanted to "rebut one falsehood I saw being stirred by various of all our political opponents yesterday".
He said: "The suggestion that we may depart the European Union but leave one part of the UK behind still inside the single market and customs union.
"That is emphatically not something the UK government is not considering.
"So, when the first minister of Wales complains about it or the first minister of Scotland says it is a reason to start banging the tattered drum of independence, or the mayor of London says it justified a hard border around the M25, I say they are making a foolish mistake.
"No UK government would allow such a thing, let alone a Conservative and Unionist one."
In Cardiff Bay, UKIP's Welsh Leader Neil Hamilton said Monday's failure to reach agreement with the EU showed a "handful" of DUP MPs had more influence than the Welsh Government.
Plaid Cymru said the "solution to the border problem is for the UK to stay in the [EU's] Customs Union".
Party leader Leanne Wood said: "Our MPs have consistently voted in favour of this in Westminster, but there has been a failure by Labour MPs to protect Wales' interests in the way they vote."
"We are facing a weak and divided Tory government, but Labour has allowed a consensus to be built over leaving the single market and the customs union.
"Labour is failing to act like a proper official opposition in Westminster on this matter. It now needs to get its act together and work in the Welsh national interest."
Carwyn Jones conceded that "there'll be different views in my party in London and those views are well known."
"But my view is, as first minister, that we are best served by staying in the customs union and having that access to the single market," he said.