Tony Blair has insisted that British overseas aid "really does work" and is helping to save hundreds of thousands of lives.
Defending the Government's controversial policy of protecting aid spending despite cuts across the rest of Whitehall, the former prime minister said that health programmes in the developing world were especially effective.
Speaking from Busan, South Korea, where he is attending a high-profile international conference in aid effectiveness, Mr Blair acknowledged that people questioned such spending when domestic budgets were tight.
"Sometimes, particularly when budgets are stretched back home, people say: 'Should we really be spending this money on aid?'" he told BBC Radio 4's Today programme.
"But if you take the money spent for example on the global health initiative, it's quite remarkable the progress there has been over the past few years.
"There have been millions of lives saved as a result of access to HIV Aids treatment - the measles vaccination programme funded by countries like the UK has cut deaths from measles by around half.
"So I totally understand when people say shouldn't we spend this money at home not abroad. But it's just worth emphasising to people that this money really does work, particularly in things like health programmes when they are done in conjunction with other institutions. They make a difference and we can measure that difference in hundreds of thousands of lives."
The International Development Secretary this week reasserted his commitment to protecting the aid budget, despite expectations that Chancellor George Osborne will struggle to eliminate the structural deficit as soon as he initially intended.
Despite objections from some Tory backbenchers, the coalition has promised to spend 0.7% of national income on foreign aid by 2013.
Andrew Mitchell told The Financial Times: "The Prime Minister, the Chancellor and I have made it absolutely clear that we stand by this commitment, and that we won't balance the books on the backs of the poorest people in the world."