Conservative MP Patrick Mercer, a former Army officer, said security and overseas aid were "inextricably linked".
He told BBC Radio 4's Today programme: "I absolutely understand the need for overseas aid although not necessarily at this level.
"But I do see that so much of the aid we have attempted to spend in the past in places like Iraq and Afghanistan has not been delivered as effectively as it might because of the lack of a benign security environment.
"If that means more money has to be spent on defence in order to increase the efficacy of overseas aid spending, I'm all for it."
Oxfam's head of policy Max Lawson told BBC Radio 4's Today programme the aid budget should be spent on "hospitals and not helicopter gunships".
The millions of people up and down the country who support the fantastic stance the Government is taking, protecting the aid budget when every other G8 nation is not doing that - they expect this to be spent on schools and not soldiers.
So we cannot see any penny diverted into the military.
It's a very small proportion of Government spending, we think it's great the Government is doing it and we think British people expect this to be spent on hospitals and not helicopter gunships.
The Prime Minister has said the government is considering spending money from the aid budget on peacekeeping and other defence-related projects.
Such a move would see millions of pounds being diverted from the Department for International Development to the Ministry of Defence.
Speaking to reporters on his way back from India, David Cameron said he intends to protect all £10 billion of Britain's aid budget, 0.7% of national income, but that he was "very open" to the idea of pooling resources between departments.
He said the money would comply with international aid spending rules and not be used for combat mission or equipment.
Despite India’s impressive economic progress, 1.6 million children died in India last year - a quarter of all global child deaths. We agree that in the longer term, aid to India should be phased out as the country continues to develop, but we believe that the poorest children will need our ongoing help, and to cut bilateral aid in 2015 is premature.
We welcome the UK’s commitment to provide technical assistance post-2015, and believe that even if aid is cut to the Indian government, the UK should explore ways to support Indian non-governmental groups that address the needs of the poorest and their work tackling the tough issues that are the obstacles to wider progress – children excluded from health and education because of gender or caste, child and maternal mortality and women’s and girls’ rights.
We welcome the UK’s pledge to commit 0.7% of GDP to foreign aid, and recognise their leadership in development.
– Kitty Arie, Save the Children’s Director of Advocacy
After reviewing the programme and holding discussions with the Government of India this week, we agreed that now is the time to move to a relationship focussing on skills-sharing rather than aid.
Having visited India I have seen first hand the tremendous progress being made. India is successfully developing and our own bilateral relationship has to keep up with 21st Century India. It’s time to recognise India’s changing place in the world.
It is of course critical that we fulfil all the commitments we have already made and that we continue with those short-term projects already underway which are an important part of the UK and Government of India’s development programme.
– International Development Secretary Justine Greening