Wealthy nations still have much to do to tackle famine, conflict and disease in Africa, Tony Blair has said.
Mr Mandela and Mr Blair discussed a range of issues
He said initiatives like the agreement on aid and debt relief reached at last summer's G8 Summit at Gleneagles showed the world had "woken up" to the issues.
But he said Africa's leaders also had to work to ensure "good governance".
The prime minister, who was speaking in South Africa at a summit on trade and development, later held talks with former president Nelson Mandela.
The UK put Africa alongside climate change as the policy priorities of its leadership of the G8 last year.
The summit at a game lodge north of Pretoria, brought together a group of centre-left leaders including South African president Thabo Mbeki, New Zealand prime minister Helen Clark, and Brazilian president Luiz Inacio Lula da Silva.
"Has the world woken up to these issues? Yes it has. Have we done enough about them? Obviously not," Mr Blair said in an interview on South African television.
"There's no sense in leaving Africa as the only continent anywhere in the world which has gone backwards in the last few decades."
He said World Trade Organisation negotiations that sought to open up western markets to poorer nations "could go a long way" to help Africa.
Mr Mandela later welcomed Mr Blair to his home.
"We spoke about the work that we are doing in Africa. the relationship between both our countries, the G8 Summit last year and what we are doing to follow it up and things that need to be done this year," said Mr Mandela.