China will provide $43bn (£27.4bn), the highest contribution among the Brics nations, to the International Monetary Fund's (IMF) firewall, it has been revealed.

Brics nations include Brazil, Russia, India, China and South Africa.

India, Russia and Brazil pledged to increase their contribution to $10bn each, while South Africa agreed to a smaller amount.

Earlier, leaders of the Brics nations met separately to decide on the size of their contributions, as they vied for a greater role in the western-dominated fund. The major emerging economies are demanding more voting rights to reflect their growing power in the world.

"These new contributions are being made in anticipation that all the reforms agreed upon in 2010 will be fully implemented in a timely manner, including a comprehensive reform of voting power and reform of quota shares," the Brics nations said in a statement.

"Emerging economies are bailing out Europe and deserve a seat at the decision-making table. It's outrageous that a country the size of Belgium has more voting weight at the IMF than South Africa or Argentina," Bloomberg quoted Jasmine Burnley, a spokeswoman for aid group Oxfam International, as saying.

The IMF received funding commitments totalling $456bn from 12 nations, which will lift its lending power to the struggling economies. The IMF said it had secured $430bn in April.

"Countries large and small have rallied to our call for action," said IMF managing director Christine Lagarde. The new contributions will be used only after the existing funds have been exhausted, she added.

At the G20 meeting in Mexico, leaders called for an increased contribution to the IMF's crisis fund. The IMF may need more funds as countries, such as Spain and Italy, are becoming prone to the contagion effect.

Mexico, the host nation of the G20 summit, matched Russia and India in agreeing to contribute $10bn to the Washington-based lender, while others, such as Colombia, Malaysia, New Zealand and the Philippines, pledged smaller amounts.

Previous funding commitments included a $60bn contribution from Japan, as well as $15bn each from Britain, South Korea and Saudi Arabia. Contributions from European leaders totalled $200bn.