Tackling Africa's problems will be the focal point of Britain's chairmanship of the G8 next year, Tony Blair has promised.
Mr Geldof was the brains behind Live Aid
The prime minister was speaking after meeting Bob Geldof and other members of the new commission on Africa.
Among the issues on the agenda were health - including Aids/HIV, poverty, conflict, and education.
The 16-member commission will report next spring and present its findings to the G8 summit in July 2005.
Mr Blair said he hoped the report would change the world's ability to tackle Africa's problems.
The idea was to bring the problems facing Africa together rather than having piecemeal measures, he said.
"The purpose of this is to get an agenda for change which is internationally agreed," said Mr Blair. "If that happens in itself, you will then start to find the action points happening from that."
The initiative could be an "agitator" to persuade both African nations to make painful changes and spur developed countries during world trade talks, debt discussions and UN conflict resolution efforts, he added.
Tamed pop star?
Mr Geldof, who was behind Live Aid, said he wanted the commission to rule nothing out in its bid to ensure the "absolute poverty that defines Africa is alleviated".
He suggested the commission could recommend something like the Marshall Plan which helped rebuild Europe after World War II.
And he denied he had been "tamed" by joining the commission and going "inside the tent".
"I'm the one who asked for the commission, so it could be that the prime minister and the chancellor are the
ones who came inside our tent, the activist tent if you like."
But he warned it would be a "badge of personal shame" for Mr Blair and Mr Brown if, during their time in office, they failed to bring about significant improvement in Africa.
After the talks, he said he hoped the commission's work would reanimate the public debate on Africa.
"We cannot accept the idea of people dying on our screens every night for ever," he added.
UK International Development Secretary Hilary Benn, who is also one of the commissioners, said ahead of the meeting: "Africa is the only continent that has grown poorer over the last 25 years".
Mr Benn said that progress on beating Africa's massive poverty problems was not happening rapidly enough and that without much greater effort from the global community it was clear that the Millennium Development Goals will not be met.
The goals, agreed at a United Nations summit in 2000, set an agenda for tackling some of the most urgent global problems by 2015.
Among the commissioners are some high-level Africans, including Ethiopian Prime Minister Meles Zenawi and South African Finance Minister Trevor Manuel.
At the post-talks news conference, Tanzanian President Benjamin Mkapa challenged claims that bad governance was at the root of Africa's problems.
He said the commission might replicate existing proposals but could create the right political will.
Asked whether another commission on Africa was needed, President Mkapa replied: "I would ask why preachers every Sunday preach in spite of the fact that the Bible has been with us for 2000 years."
British development agencies have welcomed the new commission.
Speaking on behalf of the members of the British Overseas Aid Group (BOAG), Mike Aaronson, Director General of Save the Children said: "Africa is crippled by poverty and is a long way from reaching the UN's anti-poverty goals. Any initiative that provides real solutions is a welcome step."
This was a view echoed by Mr Benn who said that with all the problems facing Africa "surely it is better that we are talking about the situation, than if we are not".