Britain will invest almost $500 million in an international scheme to encourage pharmaceutical firms to develop vaccines against some of the common diseases which plague poorer nations.

The Advance Market Commitment, a pilot project launched on the sidelines of the G8 finance ministers meeting this weekend, guarantees to buy vaccines at fixed prices once they have been developed, giving drug companies an incentive to produce them.

"The UK is pleased to support this initiative ... which should ensure a sustainable and affordable supply of vaccines well into the future," said British finance minister Alistair Darling.

Britain, Italy, Canada, Russia, Norway and the Bill and Melinda Gates Foundation are investing a total of $1.5 billion in the project, which is being run by the World Bank, UNICEF, the World Health Organisation and the international vaccine agency GAVI alliance.

Pharmaceutical firms who sign up will be tasked with developing vaccines to fight pneumococcal diseases, which claim up to 1.6 million lives each year -- most of them children.

Firms that participate will also make legally binding commitments to supply the vaccines at lower and sustainable prices after the donor funds are spent.

The AMC scheme aims to prevent more than 7 million deaths by 2030.