Former home secretary Charles Clarke has publicly urged Environment Secretary David Miliband to step forward and challenge Gordon Brown for the Labour leadership.
He said in an interview with The Independent that he believed Mr Miliband would be a "good candidate" to succeed Tony Blair when he steps down as Prime Minister later this year.
Mr Clarke, a long time rival of the Chancellor, is the most senior Labour figure to openly call on the Environment Secretary to run for the leadership.
Mr Miliband has so far ruled himself out as a candidate, but some committed Blairites hope that he can be persuaded to change his mind, believing that he is their best hope of stopping Mr Brown reaching No 10.
Asked whether he would like the Environment Secretary to step forward, Mr Clarke replied : "Yes, I think that he'd be a good candidate and a good Prime Minister. Unlike (Tory leader) David Cameron he's got good ministerial experience in a tough spending department".
He side-stepped an offer to endorse Mr Brown as the next Prime Minister, saying: "I'll take that decision when we have a leadership election".
And he questioned whether the Chancellor could deliver on his promise to choose a Cabinet of "all the talents" if he succeeded in becoming leader.
"I think that he'd need to and should try to do so. But it's easier said than done," he said.
Mr Clarke even refused to rule himself out as a candidate, saying a leadership bid on his part was "unlikely but not impossible".
His comments will heighten anxieties in the Brown camp that the Chancellor could still face a contest from a Cabinet heavyweight.
