AS he arrived at Labour’s conference hotel in Manchester, David Miliband looked like any other drab politician as he walked past a herd of photographers waiting for Tony and Cherie Blair.

So there was some surprise among the pack when he reappeared a few minutes later in an entirely different outfit. Off had come the suit and tie, and in its place was a fashionable shirt, unbuttoned over jeans and a T-shirt, with an iPod in his hand. It was a Clark Kent-style transformation from geek to Superman.

Miliband – the secretary of state for environment, food and rural affairs – glanced up as if surprised by the presence of the photographers and turned on his heel, but not before allowing a flattering image of himself to be captured.

The photograph, which was published in newspapers last week, sent a clear message: here was a Labour politicians capable of matching the fresh appeal of David Cameron.

Miliband has emerged as the latest “any-one-but-Gordon” candidate and is now being talked about seriously as a contender to succeed Blair, who has long argued privately that his former head of policy could be a better bet against Cameron in the next general election, saying he is the “Wayne Rooney” of the cabinet.

Peter Mandelson and other “öber-Blairites”, such as Alan Milburn, would love to see Miliband give it a go. Charles Clarke, the former home secretary, is said to be prepared to launch his own “kamikaze mission”.

Miliband has been careful not to kill off the talk of a rival leadership bid. Yes, he has said Brown is an “outstanding prime minister-in-waiting”, but to those in Brown’s camp this is not enough. He compounded their anxiety by publishing what many saw as his personal manifesto – his new “I can” philosophy – in a Labour-supporting journal.

“Something strange is going on,” said one Labour aide last week. “There would be great excitement if David stood, but at the same time a gut-wrenching feeling of the dark forces within the party it would unleash an an inevitable split.”

So what is Miliband’s game? Will he stand or is he just after a top job in a Brown administration? And, if he did win, how would he fare against Cameron?

Miliband and Cameron were Oxford contemporaries; and while the Tory leader has a webcam, on which he can be seen in his kitchen doing the washing up, Miliband, alone among cabinet ministers, has his own blog.

He pontificates on subjects ranging from the Indian Oscars to his efforts to secure a “fair deal for pigeons”. For his most avid followers – or “Milfans” – he has even posted clips of himself making speeches on YouTube. Surprisingly, most of the clips have had at least 1,000 hits.

He has won new admirers, with “Gays for Miliband” and “Miliband for PM” supporters on Facebook, the trendy social networking website.

But his chirpy tone on the blog contrasts with his protectiveness about his private life. He and his wife Louise, a violinist with the London Symphony Orchestra, have been through their own heartache. Finding they were unable to conceive, the couple adopted a newborn baby, Isaac, from America in 2004.

Miliband’s wife had adoption rights in the US, because she has dual citizenship, but the arrangement raised eyebrows. The Tories infuriated him by suggesting that his application to adopt might have been fast-tracked.

Despite his apparent eagerness to appear dynamic and modern, Miliband’s quaint way with words owes more to Enid Blyton’s Famous Five than an MTV popstrel. He refers to “full lashings” of fish and chips and calls people “clot”.

His father Ralph, the son of a Red Army soldier, was a social intellectual who passed his formidable brains on to both David and his younger brother Ed, also a minister. The boys went to a London comprehensive before going to Oxford to read PPE.

His “manifesto” in this week’s New Statesman appeared after weeks spent wining and dining newspaper editors. The article was accompanied by a picture of him knocking at the door of No 10.

Miliband wrote of his desire to see a new type of politics developing, from the “I want” generation to the “I can”. He began the piece with a comment about the need for politicians to be “in tune with the times”. To some, the message was: “Forget Gordon; he’s past it.”

Polls last week suggested Labour might receive a drubbing in the local and national elections on May 3, losing control of councils in England, the Scottish parliament and the Welsh assembly. In those circumstances, if enough senior party figures called on him to stand, Miliband might do so.

But, he tells friends, he knows it would split the party, with MPs torn between the old generation and the new, and the prospect that, if Miliband won, Brown would be a crushed and very dangerous man.

Brown is said to be angry at Miliband’s failure to kill off speculation. “Miliband can’t say it’s not his fault,” said one ally of the chancellor. “He knows exactly what he is doing. He could quite easily say specifically, ‘I won’t stand against Gordon’ or that he is far less experienced than Gordon – something he couldn’t go back on. But he doesn’t.”

He has told friends he is “flattered” to be considered as a potential leader. But that is the trap several cabinet colleagues have fallen into in the past, most recently Alan Johnson, the education secretary. His “leadership bid” came to nothing after a bad party conference.

In truth this looks most like Miliband simply positioning himself for the future – a way of ensuring he gets a big job under Brown. But the current “offer” on the table from Brown is not that grand: merely being given an enhanced Environment and Energy Department after the Department for Trade and Industry is split up.

The Tories insist they would be delighted if Miliband challenges Brown, despite their public briefings to the contrary.

A Tory strategist said: “The idea is to big him up – goad him into doing it. When you put Miliband against Cameron, Cameron comes across as the statesman. That is not the case when you put Cameron against Gordon.”

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