Britain will tomorrow pledge €20m in 2007 towards a French-initiated international partnership to drive down prices and boost access to the drugs required to treat the developing world's most lethal diseases.

In a speech at the United Nations, Gareth Thomas, the international development minister, will make a 20-year commitment from the UKto Unitaid, an international drug purchase facility to tackle Aids, TB and malaria, with annual contributionsrising to €60m (£40.4m) a year by 2010 subject to satisfactory performance. He will also support efforts to encourage developing countries to use all their rights under international trade agreements to challenge pharmaceutical company patents and seek cheaper production of essential medicines from generic manufacturers. The political commitment and the size of the UK financial contribution, at just one tenth of the annual €200m to be offered by the French through a levy raised on airline tickets, is also below Norway's pledge and a little above that from Unitaid's initial developing world partners, Brazil and Chile.