Tony Blair says fighting HIV/Aids is not just a "moral duty" but is in the UK's "national interests".
Queen's back catalogue will raise funds
His comments came on World Aids Day 2003, as the UK issued a call for action to tackle the HIV/Aids epidemic that has infected 40m people worldwide.
Minister Hilary Benn announced funding to UNAids would double to £6m for 2004.
In a separate development Mr Blair has become a co-chair of the International Aids Trust (IAT) with ex-presidents Bill Clinton and Nelson Mandela.
Sandra L. Thurman, president of the trust, said Mr Blair's decision to join the non-profit organisation's advisory board was a "testament to his personal commitment" to the global fight against Aids.
The trust works with leaders from all sectors to develop strong policies and mobilise necessary resources to stem the tide of the Aids pandemic.
Mr Clinton said he was "delighted" to have Mr Blair as a partner "in the critical mission of fighting Aids globally".
Mr Mandela said Mr Blair's commitment to the trust had significantly strengthened the global response to the problem.
The prime minister said: "It is my hope that by working together we can help raise awareness, increase political will and mobilise the resources necessary to stem the tide of this epidemic."
As he welcomed his appointment, the UK government was issuing a call for action, as part of Monday's World Aids Day campaign, to ensure three million people with HIV get the drugs they need by the end of 2005.
The world's poorest countries will be targeted and officials say the so-called "3 x 5" campaign is vital if they are to save millions of lives and stop Aids from spreading.
Mr Clinton is 'delighted' Mr Blair is on the team
International Development Secretary Hilary Benn has unveiled details of the UK's drive in central London.
This includes doubling funding for UNAids from £3m to £6m, committing Britain to achieve better funding, donor coordination, HIV/Aids programmes and stronger political direction.
In an article for The Sun newspaper, Mr Blair said he was proud of the UK's record in pushing HIV/Aids up the world agenda and in the "dramatically increased financial and practical help" it was giving.
Britain was "the world's second biggest bilateral donor", after the US, on HIV/Aids, he said.
But he warned that "no corner of the world has escaped" the scourge.
"It is the biggest killer in Africa. The fastest increases in infection are in the countries of the former Soviet Union," he wrote.
"And there is no reason for complacency here in the UK. While our levels of infection remain low compared to many of our European neighbours, they are still increasing.
"We are improving treatment at home and this will be an increasing priority for international efforts.
"But with no cure or vaccination available, education and prevention - where we are putting increased effort - remain the best way to protect people."
Consequently, Mr Blair said the government was publishing the call for action, which will set out further steps to be taken as the UK prepares to take over presidency of the G8 - the world's leading industrial countries - and the European Union in 2005.
"I am determined that this country will not just step up its efforts directly to tackle HIV/Aids, but will continue to offer the leadership needed to get the world to focus on what we must do together," Mr Blair added.
But Lord Fowler, the Tory ex-health secretary, said the Department of Health had "done far too little to educate and inform" about Aids.
Nick Partridge, of the Terrence Higgins Trust, said: "Now more than ever, we must step up our efforts to tackle the epidemic in this country, as well as fulfil our responsibilities in the international fight against HIV."
Edwin Cameron, an openly gay HIV-positive South African Supreme Judge, will deliver the Diana, Princess of Wales lecture on the disease, to further mark World Aids Day.
The lecture, at London's City Hall, is organised by the National Aids Trust (NAT), in memory of Princess Diana, the charity's patron from 1991 until she died in 1997.
Actors Keira Knightly, Gina McKee and Cyril Nri, who plays Superintendent Adam Okaro in The Bill, are set to attend with human rights campaigner Bianca Jagger.
In the UK, figures suggest a 20% increase in the disease in one year, with around 50,000 now infected and a third of these unaware they have the virus.
Fundraising events will take place across the UK as campaigners renew calls for greater awareness and action to combat the disease.
Sexual health charity Marie Stopes International is urging people to send a Christmas card with a condom to their MP to call for improvements to the supply and distribution of the contraceptive in countries hardest hit by HIV and Aids.
Rock band Queen - whose front man Freddie Mercury died of an Aids related illness in 1991 - has made its back catalogue available on the internet with royalties going to fund research into the disease.