International Development Secretary Andrew Mitchell has rejected claims that the Government is putting Britain's security concerns ahead of aid priorities by trimming the number of countries which will receive assistance from the UK.
A review of international aid is expected to remove 16 countries - including Angola, Vietnam and Cambodia - from the list of those which receive direct help from Britain.
Aid charities have raised concerns that the countries which will continue to get support, such as Afghanistan and Somalia, have been chosen because they are considered vital to maintaining UK security.
World Development Movement head of policy Julian Oram told the BBC Radio 4 Today programme: "What we are concerned about is the focus on a smaller number of countries, which actually takes money away from some of the world's poorest countries, like Niger, Angola and Cambodia and channels it into countries where there is deemed to be a higher security risk to the UK.
"The securitisation of aid is a real concern under the outcomes of this review."
But Mr Mitchell responded: "In terms of the suggestion that we are securitising aid, we are dealing with parts of the world where people are doubly cursed - not only because they live in extreme poverty but also because they live in very conflicted societies."
The areas in which one-third of the overseas aid budget will be spent include countries which see 75% of the world's maternal deaths in childbirth and 75% of child deaths from malaria, he said.
The Government has committed the UK to meeting the United Nations target of spending 0.7% of GDP on aid by 2013. Total assistance is due to rise from £7 billion to £11 billion by 2015.
Mr Mitchell denied accusations that some of this increase would be achieved by redefining other activities - such as military protection of reconstruction projects in Afghanistan - as aid spending.
"Our commitment is not just to the 0.7%, it is also to the rules which govern the definitions of international aid," he said.
"We have made it absolutely clear that these are the rules which will govern British aid spending, so there is no danger of money migrating into causes which are not covered."
The recent revelation that the Department for International Development contributed towards the cost of last year's visit by the Pope did not breach this principle, because the funds did not come from the pot set aside for meeting the 0.7% target, he said.
Mr Mitchell said today's review would "end a culture which has seen large sums of money thrown at problems and focus on the results that the British taxpayer can buy".
He added: "This is about value for money. It is about ensuring that, for every pound we take off hard-pressed taxpayers, we really do deliver 100p of value.
"We have got to be able to explain and articulate to the people who are paying for this why we are spending the money."
Today's review is expected to see countries like Russia, China, Serbia, Moldova, Kosovo and Bosnia removed from the list of recipients of millions of pounds of direct British aid.
The coalition wants to focus up to 30% of overseas aid to volatile states such as Afghanistan and Somalia.
But ministers face criticism for merely freezing funding for India - which can afford its own space programme - at £280 million a year for the next four years.
World Bank and United Nations funding is also set to be cut as part of the review.
Asked about the extent of overseas aid at a time of spending cuts at home, Mr Mitchell told BBC Breakfast: "We are dealing with a scale of poverty here around the world of a completely different order.
"And we do it because it's morally right, it's about our values as a country and as a Government, and also because it's in our national interest."
On India, he added: "We are walking the last mile with India in terms of its development programme.
"Our partnership with them is part of a much wider partnership with India, which was very much revivified and rejuvenated by the Prime Minister's visit last year.
"But the work we are doing there with British leadership and British development expertise is dragging in behind it hundreds of millions of pounds of Indian taxpayers' money."