June 13 (Bloomberg) — Prime Minister David Cameron said Britain will contribute an extra 814 million pounds ($1.3 billion) toward a vaccinations program aimed at preventing deaths from diseases such as pneumonia and diarrhea in the world’s poorest countries.

Cameron made the pledge at a conference he is hosting in London today to raise billions of dollars from developed countries for vaccines and immunization campaigns. Microsoft Corp. Chairman Bill Gates told the conference that the Bill & Melinda Gates Foundation, the world’s richest charitable fund, will provide an extra $1 billion to help the program.

The Global Alliance for Vaccines and Immunisation says it needs to raise $3.7 billion between 2011 and 2015 to meet a funding shortfall partly created by demand for new and underused vaccines. It wants to immunize 243 million more children and avert more than 4 million deaths. Today’s pledge takes the U.K. contribution for the period to almost 1.5 billion pounds.

Opening the conference, Cameron defended increasing foreign aid at a time of budget austerity at home. Britain should not use the need to tackle the deficit as an excuse to duck its obligations to the neediest parts of the globe, he said.

"When you make a promise to the poorest people in the world, you should keep it," Cameron said. "This is about saving lives."

"It was the right thing to promise," he said. "It’s the right thing to do, and it’s the right thing for this government to honor that promise."

The coalition government’s commitment to increase aid spending to 0.7 percent of gross domestic product by 2013 has been criticized by Defense Secretary Liam Fox, who wrote to Cameron last month arguing the target should be an aspiration rather than a legal obligation.

—With assistance from Robert Hutton in London. Editors: Fergal O’Brien, James Kraus

To contact the reporter on this story: Andrew Atkinson in London at a.atkinsonbloomberg.net

To contact the editor responsible for this story: James Hertling at jhertlingbloomberg.net