Westminster should keep its nose out of legislation proposed by the National Assembly when new arrangements kick in next May, Dafydd Elis-Thomas has warned.
He says that once the Assembly in Cardiff agrees on proposals for new laws, then MPs in London should not be able to hold a veto.
In an interview to coincide with his 60th birthday today, the Presiding Officer says an unwritten convention should be followed - perhaps known as the Hain Convention - under which legislative proposals from the Assembly are passed automatically.
The only exceptions would be when it could be demonstrated that the proposal was beyond the Assembly's powers.
After next year's Assembly election, AMs will be able to seek permission from Westminster to legislate in specified areas. Proposals will be debated in both Houses of Parliament and voted on. If approved, an 'Order in Council' will be made, giving the Assembly permission to introduce its own legislation.
Lord Elis-Thomas said, 'There should be - let's call it the Hain Convention - an understanding that anything that emerges from here should have parliamentary time. I can't see how it could work otherwise, because anything that comes out of here would have been agreed by an elected Assembly here and the government here clearly would be prepared for it to be legislated on.
'Therefore I don't see how it makes any sense for the UK Parliament to say, 'this is not appropriate'.'
Asked whether some MPs might not think they should be allowed to block proposals they don't like, he said, 'I don't recollect many Orders in Council being blocked in my time at Westminster. Any proposal will have to go through on a vote of both Houses, and presumably the whips would have something to say about this, and the precedent they would create.
'So clearly MPs would be able to speak against the order, but I would be very surprised if a government in Westminster getting its business through would want to arrange a vote knowingly - it might happen accidentally - rejecting an Order in Council which had been proposed by an elected Assembly which had voted by a majority to do it.
'I'm assuming that when there are Orders in Council proposals emanating from government that they would be worked out between Whitehall and Cathays Park. And therefore what would emerge would be something that any government of whatever colour at Westminster would be able to live with.
'Constitutional conventions will establish themselves and one of them will be, it is my understanding, that when legislation is requested by a majority in the Assembly, it should be allowed to happen, so long as it is within the agreed competence, as agreed by Westminster.
'I can see how perhaps certain MPs at Westminster might want to speak against a certain proposal for an Order in Council in debate, but I would be very surprised if a government chief whip or convenor of parties in the Lords would muster their forces against.'
Asked how ordinary people could be persuaded of the value of constitutional change in delivering real improvements to their lives, he said, 'There is no distinction in my mind between having a good constitution and having a better quality of life for people.
'The one implies the other, because the better democracy is, the better delivery of public services, the better people's lives will be.
'Also, the better democracy, the more understanding they will be of those issues which globally and internationally affect all of us, especially the environment and global warming and international peace and security.
'These are issues which daily affect the lives of all our constituents, so trying to get a better opportunity for members to express themselves in this wonderful Senedd building is to do with making sure people's voices are heard.
'Every day, there's a trick question I will ask if I'm able to of colleagues working here - of civil servants, soon to be Assembly staff. The question is, 'Who do you work for?'
'The simplistic, short, wrong answer is, 'My line manager'. The sycophantic one is, 'I work for you, Presiding Officer'. The right answer is, 'I work for the people of Wales' - and that applies to all of us.
'None of us has a right to be here. Our right to be here depends on our determination to do our work properly, whether we are elected members or appointed staff. We are all here on a mission - which is to improve the quality of life for the people of Wales.'
Secretary of State Peter Hain's Wales Office last night repeated its official line in response to Lord Elis-Thomas's comments. A spokesman said, 'The Government of Wales Act grants the Assembly much greater power to determine the detail of devolved laws for Wales. Parliament will continue to decide the principle of giving new powers to the Assembly, in line with the settlement that the people of Wales voted for in 1997.
'We anticipate that MPs will conduct detailed scrutiny of proposals for new powers, just as they do now. In particular, they will play an active role in examining the broad principles and the scope of the powers. It will not just be a question of Parliament rubber-stamping requests from the Assembly.'