Lord Elis-Thomas: 'Wind up Wales Office'
Welsh assembly presiding officer Lord Elis-Thomas has said the Wales Office should be wound up.
He told BBC Radio Wales after the Yes vote in the referendum on assembly law-making powers, the sooner the department was gone "the better".
Welsh Secretary Cheryl Gillan said he was following "a separatist agenda".
Shadow Welsh Secretary Peter Hain said Lord Elis-Thomas was "acting above his pay grade" and "out of touch with the people of Wales."
The Wales Office is based in Whitehall in London, with another office in Cardiff, and is headed by the Welsh Secretary.
It was set up in 1999 to ensure the smooth working of devolution, and is described as "Wales' voice in Westminster and Westminster's voice in Wales".
It previously handled the assembly's request for new law-making powers.
Following last week's referendum, the assembly no longer needs parliament's approval before passing legislation in the 20 policy fields that are devovled to it, such as health and education.
Lord Elis-Thomas told the Sunday Supplement programme: "Now that the responsibility of ministers for administration of policy and indeed for legislation is now here, it makes more sense for us to be organised in a proper inter-governmental and inter-parliamentary way.
"That is assembly to Westminster, government to government.
"That would mean, I think, winding up the Wales Office and as far as I'm concerned the sooner the better.
"I would like to start operating in the new way after the 5th May election."
Welsh Secretary Cheryl Gillan said it was not up to the presiding officer, who she also sat in the House of Lords too and liked that connection to the rest of the United Kingdom.
"He's 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," said Mrs Gillan.
"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."
Mr Hain said: "I'm pleased that Cheryl Gillan and I agree on the future of the Wales Office.
"Dafydd Elis-Thomas is pursuing a separatist agenda, acting above his pay-grade and is out of touch with the people of Wales."
Earlier on Twitter he said he believed Lord Elis-Thomas "should be concentrating on his day job if he wants to keep hold of it."
Former Welsh Secretary Ron Davies said constitutional reform has been on the agenda for a long time and Wales having primary law-making powers would speed up that process.
But he told BBC Wales a figurehead is still needed and believes there will eventually be a secretary for the regions who would look after Wales, Northern Ireland and Scotland.
"It's probably a bit premature to say in a cavalier way, well we've got to get rid of the Wales Office but the role of the Wales Office will undoubtedly change."
Mr Davies, now a Plaid Cymru councillor, said Wales will need to make its voice heard at a UK level and the Wales Office has a role in that but "whether it needs to continue in its existing structure is up for grabs".