Chancellor Gordon Brown has said there is no "deal" going on between himself and the prime minister over running the country between them.
Mr Brown said he would be happy to have a leadership contest
Asked directly about newspaper reports of a "dual premiership", Mr Brown told the BBC's Sunday AM programme: "There is no arrangement such as that."
"Tony Blair makes the decisions as prime minister ... I get on with my job as chancellor," he added.
He said they were both addressing the "long-term issues facing the country".
The Sunday People reported that the two men have struck an "astonishing pact" aimed at seeing off the challenge posed by Conservative leader David Cameron.
The newspaper claimed Mr Blair will stay at Number Ten until 2008, after which Mr Brown will serve as prime minister for two years before calling a general election.
Asked about the reports, Mr Brown told Sunday AM: "There is no deal or no understanding like that at all."
"We (he and Tony Blair) get on with the job of running the country and making the decisions which matter and we do so appreciating that we have got to think about the long term."
Mr Brown was hailed as the "leader-in-waiting" by cabinet colleague David Miliband in his speech at the party's spring conference - prompting applause from the floor.
Mr Miliband, once tipped as a possible rival to the chancellor, paid tribute to Mr Brown, comparing him to footballing legend George Best.
He told Labour activists gathered in Blackpool that Mr Cameron "cannot stop talking about Gordon Brown".
'Like George Best'
"It reminds me of that film of George Best in which the other team tried to hack him off the pitch in the first 20 minutes," he said.
"And what does that tell you, that they are confident? That they are ready for the match? That they think their team are world-beaters?
"It tells me they are scared of Gordon Brown as much as they are scared of Tony Blair."
However, speaking on BBC1's Politics Show, Home Secretary Charles Clarke predicted that Mr Brown would face a challenge for the leadership rather than be allowed a smooth handover from Tony Blair.
"I would be very surprised if there weren't a leadership contest," he said.
Asked whether he would welcome a challenge for the leadership, he said: "It depends on the nature of the leadership contest and how it is conducted."
Mr Brown said on Sunday he would be "perfectly happy" to face a challenge for the leadership.
Mr Blair has given no dates for when he would step down
"If and when Tony Blair stands down ... then that is the right of the Labour Party. I would be perfectly happy if there was a contest for the leadership."
And he said the "renewal" of the party was the important issue ahead.
He would not be drawn on his likely chances as prime minister taking on Conservative leader David Cameron in an election.
"Tony Blair is the prime minister; David Cameron is simply the leader of the opposition, and I am putting my ideas forward as Chancellor," he said.
"I do think, however, that the issue is who will equip this country for the future and that is over a long, long range of issues."
Mr Blair has previously stated he will leave Downing Street before the next election, but has refused to name a date.
At the start of the year he said he believed New Labour would "continue long after I've gone".