David Cameron has indicated he will block a potential bid by Gordon Brown to become managing director of the International Monetary Fund (IMF).
The Prime Minister said his predecessor was not the "most appropriate person" to lead the IMF because he would not admit the UK had a "debt problem".
Mr Brown is reportedly hoping to take on the £270,000-a-year role but he must first be nominated by the Government.
Asked whether the coalition would veto the move, Mr Cameron told the BBC Radio 4 Today programme: "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."
The PM said it was important that the IMF was headed by "someone extraordinarily competent and capable" and praised current chief Dominique Strauss-Kahn for doing an "excellent job".
Mr Cameron 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 Cameron later offered some horse racing tips to Today listeners.
He said: "What I said about Gordon Brown, if you disagree you could go for Stormin Gordon in the 2.10 at Pontefract."
But he said he would choose Red Samantha in the same race.
Labour leader Ed Miliband defended Mr Brown's record, but accused Mr Cameron of "jumping the gun" over any potential IMF role for the former prime minister.
Speaking at a press conference in central London, Mr Miliband said: "To rule someone out even before the vacancy has even arisen seems to be going some even for him."
He added: "Gordon Brown is an eminently qualified person for that job. Let's see if the vacancy does arise, but I think he would be a strong candidate."
Mr Miliband described his old boss's record over the 2007-8 financial crisis as "outstanding", blaming the budget deficit on worldwide financial meltdown.
He said: "The Government sometimes want to tell you the deficit caused the financial crisis - I think they're wrong about that."
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