Any changes to the Welsh assembly's constitutional powers should have "a democratic mandate", Peter Hain has said.

Speaking to a Constitution Unit conference in Cardiff, the Welsh secretary argued that if such proposals were made by the Richard Commission, they would need some form of public approval.

Although he did not rule out a second referendum on the issue, it is thought unlikely that the Welsh Labour Party would back such a vote after the close result on the ballot to create the assembly in 1997.

The referendum was won by the yes campaign with a majority of slightly over 6700, on a turnout of just 50 per cent.

"I am a passionate enthusiast for devolution," said Hain.

"I am proud that I fought so hard for that referendum victory. But only because I believe that devolution will bring - indeed, has already brought - tangible benefits. I am not in favour of further constitutional reform for its own sake.

"If recommendations were made by the Commission which would require changes to the Government of Wales Act, I believe that a further issue would need to be considered, that of democratic legitimacy. The current devolution settlement for Wales followed a manifesto commitment in a general election and a referendum.

"Any major changes proposed, as well as having to demonstrate very clear, practical improvements in delivery of public services to the people of Wales, would need to have a democratic mandate."