"The IMF has said it has $250 billion available, and new instruments, to lend to countries in crisis, but this may not be enough," Brown told reporters in London ahead of talks later on Tuesday with French President Nicolas Sarkozy.
"We will consider the necessary reforms to the International Monetary Fund in the weeks ahead."
Brown said countries with "substantial reserves", such as China and the Gulf States, could do much to contribute to the fund.
"We want an international fund that is strong enough to withstand these difficulties," he said.
"We now need substantial additional reserves and we want to draw reserves from countries that have substantial reserves," he added.
The meeting with Sarkozy comes before a European Union meeting on Nov. 7 and a summit of world leaders in Washington on Nov. 15. Brown and Sarkozy have spearheaded Europe's response to the financial crisis, the worst the world has experienced in 70 years.
The IMF has conducted three high-profile rescues in the past week and is now looking at ways to get more hard currency into the hands of countries squeezed by financial market turmoil.