Even in tough times Britons are a generous people, David Cameron has said, as he defended the UK's international aid budget.
The Prime Minister has faced criticism from some sectors of his own party for ringfencing the Department for International Development budget and committing to spend 0.7% of GDP on aid programmes.
But the Tory leader said there were arguments from the "heart and head" to justify the spending - worth billions every year.
Mr Cameron spoke out in an interview with philanthropist Melinda Gates, who was guest editing the BBC Radio 4 Today programme.
Mr Cameron said: "It can sometimes be a difficult argument because times are tough here at home and we have had to make difficult decisions.
"But Britain is an incredibly generous country, the British people are generous. Whenever we have aid appeals the British people always step forward in the most magnificent way."
Mr Cameron said that even while times were tough at home, Britain had a "moral obligation" to assist the poorest parts of the world.
And he said specific programmes, such as those directed at tackling disease or child malnutrition, had tangible benefits.
The Prime Minister added: "There is an additional self interested argument which is if you want to make sure countries don't break down and we don't suffer from problems of mass migration and pandemics, problems of climate change, then actually investing money in countries like Somalia which could otherwise break up and cause problems for us at home, it's in our self interest to do that as well."