Peter Hain, who will continue to speak on Welsh matter in the Commons despite the abolition of the Wales Office, insists he can still be regarded as secretary of state.
The controversy came as opposition parties led a fresh assault over the impact of the reshuffle.
The decision to appoint Scottish MP John Reid to the position of health secretary for England and Wales has also come under fire.
In the face of constitutional criticism, both ministers took to the TV studios to defend their appointments.
“I think the politics of this is that people will judge according to whether I can deliver a better health service,” said a defiant Reid.
“When they appointed Sven Goran Eriksson as England manager, there was a huge fuss about it, but actually what people want to know now is has he been a good manager?”
Hain claimed the announcement of xxx his appointment could have been handled better by Number 10.
“It was made crystal clear to me yesterday when the prime minister spoke to me about my new appointment that he wanted me to stay on as secretary of state for Wales and I will be speaking for Wales around the Cabinet table, being Wales’s voice in Westminster and Westminster’s voice in Wales,” he said.
“The Wales Office is not being abolished, I stay as secretary of state for Wales. I readily admit that in the comings and goings yesterday this whole issue could have been communicated far more effectively from Downing Street.
“I can also see why opposition parties are climbing in on the game. But I just want to say, to particularly my Welsh Labour colleagues, that I stay as secretary of state, the Wales Office will remain and Wales’ voice, far from being sidelined, is still right there at secretary of state level round the Cabinet table.”
The move came amid mounting criticism of the decision to create a Constitutional Affairs Department headed by Lord Falconer.
Hain, who will combine his Welsh role with being Commons leader, will continue to push Welsh legislation through parliament.
His comments will be seized upon by the opposition who are angered at nature of the government’s latest structural review.
The Commons leader is traditionally meant to represent MPs in government.
Linking Hain to a Whitehall fiefdom such as the Constitutional Affairs Department will lead to fresh suspicion that the role of Commons leader has been reviewed to ensure the government gets its way in the Commons.
Hain’s responsibility for primary legislation will, say some, inevitably lead to a conflict of interest.