Two ex-Cabinet ministers have denied that their call for a debate on the future of Labour is an attempt to scupper Gordon Brown's leadership bid.
Mr Milburn and Mr Clarke have both been considered possible leaders
Charles Clarke and Alan Milburn denied "troublemaking" in the race to replace Tony Blair as prime minister.
They have launched a website, The 2020 Vision, to debate future policies with both the party and the public.
The two said they expected Gordon Brown to be the next Labour leader, but did not rule out standing themselves.
They said it was important to show Labour had not run out of ideas and to stop the Tories "owning the future".
Set the agenda
Baroness Jay introduced the launch on Wednesday of the website, which includes links to speeches, policy papers and invites comments - among MPs who have already contributed are Frank Field, Ann Clwyd, Barry Sheerman and Hilary Armstrong.
At the launch former home secretary Charles Clarke said his ambition was for the 21st Century to be dominated by progressive Labour governments.
He said Labour could not rely on past successes to win future elections, but had to spell out what they would do on issues like the environment, home ownership, constitutional reform and childcare.
He said previous Labour governments in the 1940s and 1970s had made the mistake of allowing the Conservatives to set the popular agenda.
Current debates - like Tony Blair's Number 10 based policy review and the deputy leadership race - were too inward looking and did not address the wider country, he said.
The launch, in Westminster, was attended by a few Labour MPs and peers as well as most of the political press corps.
'Flush out' rival
Neither Mr Clarke nor Mr Milburn are seen as being close to Chancellor Gordon Brown, who is currently widely seen as unbeatable in terms of succeeding Tony Blair as PM when he steps down later this year.
However, Stephen Byers, a former Cabinet member and Blair supporter, who is very close to Mr Milburn, told BBC2's Daily Politics: "The Labour Party is not the Royal Family, we don't go in for coronations.
"I hope there will be a serious contest for the leader and that means someone who is either in Cabinet or has been in Cabinet recenty and I hope that will happen."
There has been speculation that both Mr Clarke and Mr Milburn, the former health secretary, are attempting to "flush out" a heavyweight rival to the chancellor.
Mr Clarke said although the debate about the leadership of the party and the future direction of the party were linked, they were "not the same".
"This is a debate about the politics and policies of the future," he said.
"This is not about causing trouble for anybody, it's not about building up a putative candidature for somebody, it's not an intervention in the leadership process."
Mr Clarke told BBC Radio 4's World at One that Mr Brown's "general demeanour to debate in the party" had been positive when the pair met him on Monday.
However, he admitted Mr Brown had raised concerns about "timing and conduct, rather than the principle of having debate".
Mr Brown felt the debate "would inevitably be seen through the prism of the leadership election so it's difficult to debate policy," Mr Clarke said.
"That is a problem and Alan and I have worked very hard...to avoid that being the case."
Mr Brown was also concerned that it would get "caught up with that overall electoral battleground" of the upcoming elections in Scotland, Wales and England.
'Appetite for debate'
Mr Milburn, who some have speculated might launch a "kamikaze" run at the leadership, if no other heavyweight challenger emerges, also dismissed the speculation.
"That's not what this is about. If anybody wants a leadership campaign that is a matter for them, but it is not a matter for us," he said.
He said there was a "great appetite" for a debate, not just within the party, but across the country.
Mr Brown is widely expected to succeed Tony Blair
"The next election will be won, not on what we have done, but on what we are planning to do," he said.
At prime minister's questions, Tory leader David Cameron asked if Mr Blair had found the time to attend the launch - and asked why so many Labour MPs thought Mr Brown would be "terrible" as prime minister, but were not prepared to stop him.
Mr Blair replied that he was "delighted that a full policy debate is happening within the Labour Party".
He defended the chancellor's record and added: "It's policy that will determine the future of this country, we have got it, he [Mr Cameron] doesn't."
Speculation at Westminster continues to suggest some senior Labour figures want David Miliband, the environment secretary, to stand - although he has always said he believes Mr Brown would make an "excellent prime minister".
Mr Clarke and Mr Milburn acknowledged that media reporting of the launch would be through "the prism" of the leadership question, and the issue dominated the questions at the 45 minute event.
Asked if either might stand themselves Mr Clarke said he never "ruled anything out" but said he expected Mr Brown to be the next leader, and that he expected to support him. Mr Milburn's one word answer was "snap", suggesting his position was the same.
So far two contenders from the left of the party, John McDonnell and Michael Meacher have said they intend to challenge Mr Brown.
But there have been doubts whether either can get the necessary 44 Labour MPs to back them to enter the contest.