Italy and France have been accused of reneging on promises to increase aid to African nations.
Anti-poverty group One, set up by rock star Bono, said Italy had actually cut aid to Africa despite making ambitious pledges at a 2005 economic summit.
And it accused France of reducing its aid targets and cutting its aid budget.
The report, backed by figures like Bill Gates and Desmond Tutu, said Italy and France were holding back other members of the G8 group of rich nations.
In 2005, the G8 pledged to increase aid to Africa by $25bn (£15bn) by 2010 - more than doubling the 2004 level of aid to the continent.
The BBC's international development correspondent David Loyn says the research is underpinned by a fear that the global economic downturn could undo what modest progress has already been made.
Sir Bob Geldof and former UN Secretary General Kofi Annan have written a joint introduction to the report in which they talk about the global financial crisis.
They say the world's poorest people have benefited least from globalisation, but they are now suffering the most from a crisis they did not cause.
Italy 'has no credibility'
The One report concluded that the US, Canada and Japan had largely met their commitments - adding that their pledges had been relatively modest.
It said the UK and Germany had missed some targets but were attempting to put in place much more ambitious programmes than the other nations.
The report, due for its worldwide release later, is particularly critical of Italy, which is due to hold a G8 summit later this year.
"Italy has said it will put Africa at the forefront of the agenda at the G8 summit," the report says.
"Based on its performance against the [last G8 summit] commitments, it has no credibility to host discussions of such global importance."
The Africa manager of One, Edith Jibunoh, told the BBC that the G8 had performed "poorly".
"This is because of two countries in particular, Italy and France, dragging down the rest of the group," she said.
"We have estimated that in 2009... about half of the promises made will be delivered. But by 2010 they need to deliver the other half. Now Italy and France alone are 80% responsible for that shortfall."
The One group is part of the anti-poverty advocacy organisation Data (Debt, Aids, Trade Africa), set up in 2002.
During a news conference on Wednesday Italy's Prime Minister Silvio Berlusconi - who is meeting Libyan leader Muammar Gaddafi - called for decisive action from wealthy countries to help bring Africa out of its misery.
"It's a big problem that requires a big decisive response from all those who are fortunate enough to be well-off," he said.
However, he said that aid could not simply continue to pour in to Africa.
He accused some African leaders of funnelling money into their own Swiss bank accounts rather than use it to help their people.
Overall aid to Africa has increased over the last four years - and as a result 34 million children are in school and three million people now receive treatment for Aids.
But there is trouble ahead, says the BBC's Africa analyst Martin Plaut.
The report warns that at least half the African states that have had their debts cancelled are now borrowing so fast they will soon be in trouble.
And with an estimated $150bn a year being lost to Africa through corruption, some may ask whether money is running out of the continent faster than it is flowing in, our Africa analyst adds.