Clare Short has questioned how Bob Geldof's Live 8 concert will help eliminate African poverty.
Ms Short resigned from government after the Iraq war
The ex-international development secretary also said there was "lot of spin" over June's debt relief deal for some of the world's poorest nations.
She told the BBC's Question Time it was being paid for through existing aid.
Ms Short also accused Geldof of going "way over the top" in his reaction to Live 8 tickets being sold on eBay, saying: "Hubris is flying".
Ms Short told the programme: "People will enjoy the concerts because there are famous bands but quite how the concerts are going to eliminate poverty in the world is not clear.
"I think there's something wrong with the lack of African music when you've got some very famous African musicians now - it's like Bob Geldof and Tony Blair are going to save Africa at one meeting."
Mr Blair has made debt relief and aid for Africa two of his key aims for next month's G8 summit of economic powers in Gleneagles, Scotland.
But US President George W Bush has already rejected several key parts of Britain's relief plan.
Earlier this month, Chancellor Gordon Brown secured a deal with G8 finance ministers to write off billions of pounds of debt owed by African nations.
"We are presenting the most comprehensive statement that finance ministers have ever made on the issues of debt, development, health and poverty," Mr Brown said.
He added that the plan set the stage for the G8 summit, where world leaders intend "to forge a new and better relationship, a new deal between the rich and poor countries of the world".
The series of concerts that make up Live 8 will take place around the world on 2 July.
Earlier this week ex-Liberal Party leader Lord Steel said Geldof was in danger of turning his anti-poverty campaign into an ego trip.
He said some of Geldof's "populist antics" risked destroying his well-deserved reputation for raising awareness of Africa's plight.
And inviting the Pope, Dalai Lama and Nelson Mandela to be involved in Live 8 had "slight touches of megalomania".