Wales Office 'hard to justify' says Plaid Cymru leader
Plaid Cymru leader Ieuan Wyn Jones says it is "difficult to justify" having separate Cabinet secretaries for Wales, Scotland and Northern Ireland.
The roles could be merged in a single UK government department, he said.
Mr Jones was speaking after assembly Presiding Officer Lord Elis-Thomas said the Wales Office should be scrapped.
His comments sparked a row, with Wales Office minister David Jones accusing him of declaring "guerrilla warfare" on the British state.
Deputy First Minister Mr Jones called for a "proper mature discussion" about relationships between London and Cardiff after last week's referendum on the assembly's law-making powers.
The Wales Office previously handled the assembly's requests for new law-making powers.
The Yes vote in the referendum means the assembly no longer needs parliament's approval before passing legislation in the 20 policy fields that are devolved to it, such as health and education.
Mr Jones said it leaves the department - which has offices in Whitehall and Cardiff - with a "much diminished role and therefore it does call into question how long you can have the Wales Office in its current structure".
"And I think we need to have a mature debate about what is the role of the Wales Office in post-devolution Wales, Scotland and Northern Ireland," he added.
"You know, can you really justify having three departments of state - Scotland, Northern Ireland and Wales - now that powers have been devolved in the three nations?
"So there is a case to be made for having perhaps a department of state in the UK that actually looks at relations with the three countries and perhaps within that to have ministers of state at that level to deal with relationships with Wales.
"It is difficult I think in the long term to justify having separate secretaries of state for the three countries."
Lord Elis-Thomas told BBC Radio Wales' Sunday Supplement programme that "it makes more sense for us to be organised in a proper inter-governmental and inter-parliamentary way".
"That would mean, I think, winding up the Wales Office and as far as I'm concerned the sooner the better," he said.
Rachel Banner of True Wales, which campaigned for a No vote in the referendum, said the result "handed the nationalists power on a plate".
"Now Dafydd Elis-Thomas is declaring that the Wales Office and the secretary of state for Wales should be disbanded," she said.
"As we predicted, the momentum is now for a step-by-step process to separation from the UK.
"Politicians in the unionist parties will now be left wondering how they can get the genie back into the bottle."
Labour shadow Welsh Secretary Peter Hain said there would always be a need for a secretary of state for Wales.
He accused Lord Elis-Thomas of "acting above his pay grade" and of being "out of touch with the people of Wales."
Mr Hain conceded that as a result of the referendum, the nature of the post would change.
"But you need somebody around the Cabinet table tapping the shoulders of Cabinet colleagues to say: 'What about the Welsh budget?'
"If you don't have a secretary of state for Wales batting for Wales then Wales' voice will be reduced and that is a very important factor."
Welsh Secretary Cheryl Gillan said Lord Elis-Thomas was "singing to a separatist tune and I don't think that's what the people of Wales want or the businesses who invest in Wales.
"They don't want separatism, they want that confidence and maturity to allow Welsh laws to be made closer to the people of Wales but they also want that connectiveness to the rest of the United Kingdom."
Speaking on BBC Radio Wales, Wales Office minister David Jones said that as a nationalist, Lord Elis-Thomas had spent his career trying to take Wales out of the union of the UK and create an independent Wales.
"It therefore benefits him and his party to undermine the British state," said Mr Jones.
"What he was doing yesterday was really part of this process. He has, if you like, declared guerilla warfare upon the British state."