The announcement was made during the European Union (EU) summit in Brussels.
The pronouncement is sure to provide a boost to UN climate talks in Denmark.
Addressing the media, Brown said, "This is the time for more than just speaking words. This is the time to act."
"Long-term support is required for developing countries," Brown noted, while talking to media with French President Nicolas Sarkozy standing beside him.
The duo further said that they want the EU to agree to a 30 percent emissions reduction from 1990 levels over the next decade.
"France and Britain want an agreement to cut (EU) emissions by 30 percent by 2020. We are the two countries pushing Europe to pursue this ambitious goal," Sarkozy added.