He said the IMF would adopt an ambitious plan to give greater weight to more dynamic economies by rebalancing quotas, which determine how much a member contributes to the fund, its voting rights and access to financing.

But Rato, a former Spanish economy minister, said the plan would have little impact on the actual policy decisions of the International Monetary Fund, which has a mandate to help countries achieve macroeconomic and financial stability.

"It's important, not so much to change the direction of the institution but to give it stronger credibility, that the most dynamic economies get the representation their real economic weight represents in the world," he said.

Rato said he expected the IMF to agree at its annual meeting in Singapore in September to embark on a two-year programme of reform by taking some important steps, following its decision in April to start drawing up concrete proposals.

"These would include immediate action on quota increases for a few countries whose quotas are most clearly out of line with their weight in the global economy," the IMF managing director told journalists in Tokyo.

"But I would also want our members to agree in Singapore to move during the next two years on more fundamental changes. Those changes would include a further round of ad hoc quota increases for under-represented members following a review of the formula that is used to calculate quotas," he added.

Rato declined to say which countries were likely to see the greatest voting boost although China and South Korea are seen as potential beneficiaries.

At the same time he said it was important to protect the voice and representation of lower income countries by raising the number of basic votes assigned to members regardless of their quota size.

"This is an ambitious and broad programme. My idea is that governors will accept it and make a specific backing of it at Singapore, and that over the next two years it will be implemented by the board and by management," he said.

Long dominated by the United States, European countries and Japan, the IMF has been locked in debate over how to better represent emerging economic heavyweights such as China, which now has fewer Fund votes than Belgium.