Sachs urged that the leaders at the summit honour their aid commitments to the continent despite the global economic crisis.
"South Africa by itself represents South Africa, and it can help to look after all the rest but it is not able to look after all of Africa," he says.
"Africa needs representation."
As leaders gather in London for the G20 summit
, Sachs says it is "shocking" that most of rural Africa does not have electricty. Leaders, he says, must agree that a country in the 21st century cannot develop without it.
"Yet electricity does not reach hundreds of millions of people. Rural africa's basically without electricity. You can't run a clinic, you can't have a proper school, you can't have a mill for grains, you can't have small business development if there's no electricty."
If African countries have money to spend, then they must invest in projects now. But the terms on which these investments go forward, depend on rich world, as according to the Millenium Development goals, Sachs adds.
"Africa would govern properly and develop serious programmes of national development and strategies for poverty reduction and the rich world would help finance that," he says.
So far, aid has increased only marginally, Sachs says, even though it has been mentioned at every G8 meeting since 2002. Despite the global economic crisis, the wealthier nations must do what they can to help those without means, he urges.
"The rich countries, now a little less rich then they were but still rich compared to the rest of the world, are way off track in honouring their commitments," he says. "And this is a tragedy for the billion people who depend on a true partnership, not just on words."