The government needs to do more to justify increasing foreign aid at a time when a poll shows more than three quarters of the public want it cut, Andrew Mitchell has warned.
The ex-international development secretary warned voters would increasingly believe the policy was a stunt to "detoxify" the Tories without a more concerted effort to explain the benefits to the UK.
Asked in a ComRes survey for ITV News which areas of public spending should be raised and which cut between now and 2015, voters said the overwhelming priority for extra cash was the NHS.
In only three areas - local government, public sector pensions and aid - they put cuts before increases with only 8% wanting overseas help to rise and 16% supporting the status quo.
The Government is committed to meeting a United Nations aim of spending 0.7% of GDP and has protected the international development budget from swingeing spending cuts being imposed to tackle the deficit.
Chancellor George Osborne spoke out strongly in favour of the pledge yesterday - saying at the meeting of G20 finance ministers in Moscow that it would help poorer countries tackle tax avoidance.
But Mitchell, who was forced out of his job as chief whip over a claim - which he denies - that he called police officers "plebs", said more needed to be out there making the case.
"Every single member of the Cabinet should be out explaining why we stand by this commitment, why we are doing it, why it really matters for Britain because if they don't, the public will conclude that this is some sort of detoxification measure for the Conservative Party," he told BBC Radio 4's Westminster Hour.
"It is absolutely not...it is about the interests of our country and future generations of people in Britain. It is about making our world more safe, more prosperous and secure and it is about making Britain safer and more secure.
"It is quite right for a sceptical public, who are seeing the reductions in public spending being made very close to home, to say if money is going to be being spent overseas we need to explain precisely why and what good it is doing.
"But equally we have promised the poorest people in the world that we will be at their side. That was a British promise made by all three of the major political parties and it's right that we should stand by that commitment."