Gordon Brown today pledged almost £2.4 billion to combat poverty, including £1 billion to fund vaccines for children in the poorest countries.

The Chancellor’s extraordinary commitment is more than double the money donated to the same fund yesterday by Bill Gates, the world’s richest man. If other nations respond, five million lives could be saved between now and 2015, Mr Brown said in a speech in London.

He will now work to persuade the other G7 nations, particularly France, to match Britain’s donation.

The £960 million funding over 15 years was announced in the speech to a seminar organised by the Department for International Development and the UN Development Programme.

In addition, Mr Brown also pledged £1.4 billion by 2008 to fund education programmes, with a focus on girls’ schooling - adding up to £2.4 billion of aid commitments over the next 15 years.

The Chancellor said the response to Asian tsunami had shown the willingness of British people to help others around the world.

He said: "Far from there being compassion fatigue, perhaps for the first time, millions more people are understanding just how closely and irrevocably bound together are the fortunes of the richest persons in the richest country to the fate of the poorest persons in the poorest country of the world."

The Chancellor, recently returned from a trip to Africa, said: "No statistics, however depressing, can prepare you for the hopelessness and human loss that lies behind the numbers but I saw too - amidst terrible suffering - hope, optimism and a determination, especially among mothers, to see things change. From the suffering in Africa I witnessed and the potential in Africa I could glimpse, it is our duty to act and to act urgently."

He added: "Surely it is our belief that every child is precious, every child is unique, every child is very special, every child deserves our support, no child should be left out. Every child matters. Every child counts."

Mr Brown warned that the UN's Millennium Development Goals of halving poverty, providing primary education for all and preventing avoidable infant deaths would not be achieved for decades beyond their targets.

The vaccine commitment is part of a five-point plan on debt relief, aid, trade, education and health, designed to put the international community back on track to meet the millennium goals set by the UN.

Not to be outdone, Tony Blair today addresses the world economic forum in Davos, Switzerland, claiming that wealthy nations cannot afford to ignore Africa or climate change.

The week has turned into a kind of bidding war, benefiting children in Africa, and largely funded by the British taxpayer.

Yesterday The Times reported that Mr Gates, the Microsoft billionaire, was to give $750 million (£400 million) to the Global Alliance for Vaccines and Immunisation.

Norway also pledged $290 million, but Mr Gates said that this was "just a downpayment" and challenged other rich countries to meet the World Health Organisation target of ensuring 90 per cent of children have inoculations by 2015, saving 10 million lives.

Mr Brown’s pledge is unusual in size and the 15-year time span. Some of it will be drawn from funding already given to the Department of International Development to spend up to 2008. "It will rise steadily after that, but the key thing is that this money will be committed and retained," an aide to Mr Brown said.

The reason for the long-term commitment is that Mr Brown wants to use the donation to launch his brainchild: the International Finance Facility (IFF). This is a way of doubling aid by allowing borrowing against governments’ long-term spending commitments. The Global Alliance on Vaccines and Immunisation could use Britain’s committment to spend more money in the short term.

However, the commitment will probably outlive both Mr Brown and Mr Blair’s time in power so it requires the support of the Conservatives and the Liberal Democrats.

The Treasury said that opposition parties supported the principle of the IFF. "We’ve deliberately given this binding commitment, so that if the Global Alliance want to go ahead and launch a mini-version of the IFF, they can go ahead and do it," said the Treasury.