The government would have to report every year on whether they were meeting their promises to developing countries under plans being backed by ministers.
Mr Benn promised a "frank debate" on aid from the UK
Labour backbencher Tom Clarke had proposed the new laws but his private member's bill has no chance of being passed without government support.
International Development Secretary Hilary Benn says he welcomes the idea.
Live Aid founder Bob Geldof says people want to know if promises are being met and whether aid money is working.
'Making a difference'
Mr Clarke said the new law would ensure there was no "backsliding" on the commitments made by Tony Blair last year at the G8 summit at the height of the Making Poverty History campaign.
Mr Benn told the Guardian Unlimited website he and other ministers would support the idea.
He said: "As more aid comes through the system and as there is greater interest in what we can do to help development to occur in Africa - people will increasingly ask how we can be more effective - what difference is it making and how do we know the money is fulfilling the purpose it was intended."
Mr Geldof said it was extraordinary ministers did not already have to deliver the annual report and that it was currently left to MPs to ask individual questions.
"We need to know what is happening with all these promises and money that is flowing," he said.
"We need to know where it is being spend, how much of it has been delivered, is it working?"
The government's backing comes after Mr Benn announced the government was to conduct the first full review of the UK's aid policy for five years.
Mr Benn promised a "frank debate" on aid from the UK would be followed by a government White Paper policy document.
But he also criticised Make Poverty History and other campaigns for underestimating the impact of economic growth on developing countries.
"There is little real debate about growth," Mr Benn said in a speech.
"Many of these campaigns say little explicitly about the creation of more and better jobs for poor people.
"Ask poor people where the best prospect for escaping poverty lies - they'll tell you it is through self-employment or business - a good job.
"Poor people are the private sector, they are the farmers and small businesses that we are trying to help."
He said Make Poverty History and other campaigns last year had focused on more and better aid, debt relief, international obstacles to trade, education, HIV/Aids.
Mr Benn said a lot had been achieved last year including an EU agreement to commit 0.7% of the UK national income to aid by 2015 and a G8 agreement to universal access to AIDS treatment for all by 2010.
A clear plan was needed to translate the promises of 2005 into further action, he said.
Oxfam campaigns director Adrian Lovett said it was surprising to hear Mr Benn criticise Make Poverty History.
He said Oxfam, a founder member of the campaign, knew trade could be an essential engine for growth.
"Millions of people, not just in Britain but around the world, expected governments to take the challenge and change the world trade rules when they met at the World Trade Organisation in December," he said.
"Sadly, they failed - but those millions will continue to demand the reform that will give people the chance to work their way out of poverty."
But Conservative shadow international development secretary Andrew Mitchell said Mr Benn was right that economic growth and trade was a key factor in reducing poverty.