Gordon Brown's hopes of heading the International Monetary Fund were dealt a serious blow as David Cameron indicated he was ready to block his predecessor's appointment to the role.
The Prime Minister said Mr Brown was not the "most appropriate person" to take over as managing director of the IMF because he failed to understand the dangers of excessive debt.
His intervention raised the prospect of a UK veto amid heightened speculation that Mr Brown is emerging as a leading contender to take over from Dominique Strauss-Kahn who is deciding whether to be the socialist candidate in the French presidential elections next year.
Labour leader Ed Miliband insisted the former prime minister and chancellor would be "eminently qualified" and a "strong candidate" for the £270,000-a-year job.
But, asked whether he would veto the move, Mr Cameron said: "I haven't spent a huge amount of time thinking about this but it does seem to me that, if you have someone who didn't think we had a debt problem in the UK when we self-evidently do have a debt problem, then they might not be the most appropriate person to work out whether other countries around the world have debt and deficit problems."
Speaking on BBC Radio 4, the Prime Minister suggested that the IMF should look to "another part of the world" for its next leader in order to increase its global standing.
"If you think about the general principle, you've got the rise of India and China and South Asia, a shift in the world's focus, and it may well be the time for the IMF to start thinking about that shift in focus," he said.
"Above all what matters is: is the person running the IMF someone who understands the dangers of excessive debt, excessive deficit?
"And it really must be someone who gets that rather than someone who says that they don't see a problem."
Mr Miliband accused Mr Cameron of "jumping the gun" over any potential IMF role for the former prime minister.