Meeting to discuss the EU's position for the G20 summit later this month, the leaders resisted pressure from Washington to shrink the IMF's key panel, possibly at the expense of European countries.
The United States has pressed European countries to reduce the eight seats they occupy on the 24-member decision-making IMF board, even possibly merging to a single chair to make way for changes to the quotas of developing countries.
"The current size of the IMF executive board reasonably well reflects the trade-off between inclusiveness/legitimacy and the effective functioning of the Fund," EU leaders said in a statement.
The leaders were more open towards giving emerging economies such as China or India greater voting power at the Fund and the World Bank, known as the Bretton Woods institutions after the town where they were conceived.
But the shift in voting power should increase the votes of under-represented countries in relation to the over-represented, the leaders said, rather than moving votes from developed countries to emerging economies - a nuance in wording that changes which countries would lose influence.
Spain is under-represented in the Fund, while Argentina and Saudi Arabia are over-represented, EU sources have said.
"The reforms of the Bretton Woods institutions should increase the voice, quota and representation of under-represented countries, based on objective criteria reflecting the changes in the world economy," the EU statement said.
The leaders confirmed a decision by their finance ministers to raise the EU's contribution towards extra funding for the IMF to 125 billion euros ($184 billion) from 75 billion pledged in March.
The rise is a consequence of leaders from the Group of 20 industrial and emerging countries tripling, rather than doubling as initially expected, the amount of IMF resources to $750 billion at their summit in April.
The IMF, lender of last resort to governments, needs more resources to help a number of countries handle the worst economic crisis since the Second World War.
In July, EU finance ministers disagreed on whether the Union should have a single seat at the IMF and other institutions, although they agreed to try to speak with one voice at those fora.
(EurActiv with Reuters)
