Foreign secretary David Miliband, hotly tipped as a future leader of the Labour party, called for a radical change in politics on Wednesday, a move interpreted as laying the groundwork for a leadership challenge.

Writing in the Guardian newspaper, Miliband listed some of the government's failings over the past 10 years and said the party needed to overhaul its ideas if it was going to win another election against the Conservatives.

"To get our message across, we must be more humble about our shortcomings but more compelling about our achievements," Miliband wrote, adding that the times, with Labour lagging far behind in opinion polls, "demand a radical new phase".

"New Labour won three elections by offering real change, not just in policy but in the way we do politics. We must do so again," the 43-year-old said.

With Prime Minister Gordon Brown unpopular in the polls and the party having lost a once-safe seat in an election last week, speculation has grown rapidly that Brown's leadership could be challenged, barely a year after he succeeded Tony Blair.

In his opinion piece, Miliband did not mention Brown once, instead focusing on where he thought Labour could have done better and needed to change tack if it was going to give the resurgent Conservatives a run for their money.

"With hindsight, we should have got on with reforming the National Health Service sooner. We needed better planning for how to win the peace in Iraq, not just win the war," he said.

"The modernisation of the Labour party means pursuing traditional goals in a modern way."

The Times newspaper interpreted Miliband's move as pre-positioning for a leadership challenge, saying such an opinion piece could only intensify pressure on Brown.

"Mr Miliband will be effectively defying Mr Brown to sack him - a move that could hasten the prime minister's own end," the paper said.

The Guardian was not so firm in its own interpretation of Miliband's move, saying he offered "no overt disloyalty, nor does he suggest Brown is the only figure capable of taking the party through difficult economic times."

Miliband, who has youth and a polished style on his side, is one of several ministers seen as potential leadership challengers. As foreign secretary he has a high international profile, but is less well connected with Labour's rank and file members among the unions.

Political analysts believe the time is ripe for a challenge as the party's popularity under Brown has fallen to around 25 percent, near historic lows and around 20 points behind the Conservatives.

With an election due by May 2010, the logic goes that a new leader should be found now, allowing time for them to try to revive the party's fortunes before a vote.