Poverty campaigner Bob Geldof has urged Gordon Brown to stump up £400m in new money to help developing countries.
Geldof is now more known for his charity work than his music
Appearing alongside the chancellor at the Labour conference, the ex-Boomtown Rats star said nations were falling behind on their aid pledges.
He suggested the UK might need to fill the gap left when countries like Italy were unable to fulfil their promises.
Mr Geldof also said President George Bush's plans to fight Aids by promoting fidelity were working in some areas.
He admitted his comments would anger some of "my lot" of aid campaigners who wanted the focus to be on using condoms.
The chancellor joked that the Live Aid founder was both his "mentor and tormentor".
Mr Geldof has said he wanted to "nail" Mr Brown as he pressed for new commitments in next summer's comprehensive spending review, which sets the government's budgets for the next three years.
He said £110m had been spend on international development last year but the UK, like other nations, was "falling behind".
"To get back on track, the comprehensive spending review really needs to commit around £400m in new money," said Mr Geldof.
The UK Government aims to be giving 0.7% of its GDP in aid to developing countries by 2013.
But Mr Geldof suggested that target might need to be brought forward and met by 2010.
"I don't see how Italy along can meet its commitment," he said. "I don't see how their economy can take the strain.
"We may have to step into the breach as we have done before as we did so remarkably last year."
Faith fidelity schemes
Mr Geldof said increased use of condoms was one reason why Aids had stabilised in Africa.
But he also said Mr Bush's President's Emergency Plan For Aids Relief (Pepfar) was proving highly effective in some places.
The $15bn programme comes with strings attached - notably in diverting a third of the funds to faith based groups which preach abstinence.
Mr Geldof said that as an atheist he was not going along with this "if you like fundamental Christian agenda".
But he had seen slogans such as "safe sex" and "fidelity" marked in chalk on huts in rural Africa, where women often had no power to refuse sex.
"It's given women a weapon they can use," he said. "That may sound odd but sometimes you encounter cultures that are not like our own."
School 'slavery' call
Mr Geldof said his "mob hate me saying this" and he was not saying others should follow the same path - but it had helped women to stabilise their relationships and perhaps their health.
The former rock star also gave a dose of his characteristically strong language, using the f-word as he raged about the fact that 90% of children in Africa went to bed hungry each night.
More had to be done on building the capacity of African Governments to build schools and hospitals.
The chancellor said 10 million of children's lives could be saved through a new deal with the Gates Foundation on vaccinations in developing countries against diseases like tuberculosis.
And he said a scheme headed by Nelson Mandela to drive for a school place for every child in the world would be a fitting way to commemorate next year's bicentenary of the abolition of slavery.
The plan would "abolish what is a slavery for children - that they do not have the right to education".
International Development Secretary Hilary Benn told delegates Labour's tripling of the aid budget was lifting 5,000 people out of poverty every day.