Tory Assembly leader Nick Bourne, who was at the forefront of the campaign against devolution, said today that he would join the campaign to get more powers for Cardiff Bay.
Ahead of the Welsh Conservatives annual conference this weekend, Mr Bourne said he was wrong when he warned about the dangers of setting up the Assembly.
The Government of Wales Bill, going through Parliament now, will give the Assembly Scottish-style powers after a referendum.
In the meantime, it will beef up the Assembly, allowing Westminster to delegate law-making powers to AMs.
Mr Bourne told a press briefing today he had had a change of heart since 1997 and will call for a yes vote when the referendum is held.
There is only one way forward, he said.
We have got a devolution settlement. When it comes to the next General Election, the Assembly will have been around for 10 years.
He said Wales had to look for a sustainable future.
I am not sure I would be leading a yes campaign, though I would certainly be taking part in it.
Although he was right to warn devolution would be expensive, he added: I was wrong that it was going to weaken the union and it would lead to nationalism on the march.
I put my hand up and say I was wrong. I have said that previously.
The Tories have said all changes to the Assemblys powers should require public consent through a referendum.
Mr Bourne said a new settlement could only be sanctioned, endorsed and entrenched by a referendum.
Mr Bourne said Labour was split on devolution because giving law-making powers to the Assembly would require more AMs and fewer Welsh MPs.
He also signalled he would be prepared to work in a coalition government after next years Assembly elections.
The Tories have worked with Plaid Cymru, the Liberal Democrats and independent AMs to inflict a series of defeats on the minority Labour government.
He said the 2007 election would probably result in either a Labour-led coalition or a coalition involving the present opposition parties.
I dont think its sensible at this stage to rule out anything, Mr Bourne told reporters.
As much as I get on with Rhodri (Morgan) in a personal way, I dont think there will be many policy areas where we can agree.
He said he was glad David Cameron was leading the party back to the political centre ground, following the publication of the Tory leaders declaration of Conservative values today.
The Tories could not get into power by encouraging fewer and fewer people to become more and more conservative.