By David Loyn
International development correspondent, BBC News
Mr Brown hosted African leaders in London ahead of the G20 summit
African leaders have warned that parts of the continent could be plunged back into conflict if they are not helped to recover from the global downturn.
The stark warning came as they gathered in London to put their case ahead of the G20 summit next month.
The scale of the crisis faced by Africa because of the economic downturn is only now becoming apparent.
The head of the African Development Bank, Donald Kaberuka, called it an "emergency" at the meeting in London.
British Prime Minister Gordon Brown heard tales of woe from across the continent - 500,000 thrown out of work in copper mines in Zambia, farmers losing jobs in Tanzania when the cotton price halved, foreign receipts down everywhere because of a cut in tourism and the reduction in remittances sent home by workers living abroad.
'Spend now or pay later'
The prime minister of Ethiopia, Meles Zenawi, made a case for the richest countries in the world to invest in Africa for their own self-interest.
He said that it made sense to invest in Africa for the state of the world economy, since the money went further.
"The global stimulus impact of every dollar spent in Africa is higher than if it is spent in the US or the UK," said Mr Zenawi.
Countries like his own that have come out of conflict in the recent past could find their stability threatened by the downturn.
If recent progress was threatened then some countries "could go under and that would mean total chaos and violence," he added.
Stability in another fragile post-conflict country, Liberia, is also threatened, according to President Ellen Johnson-Sirleaf.
She said that it made sense for the richer countries in the world to fund the poorest now, since it would cost much less than paying for peacekeeping operations later.
There was a need to "sustain the gains made by African people over the years with such sacrifice", Ms Johnson-Sirleaf said.
There has been significant progress in development in a number of African countries in recent years, mainly because of big investments from China, cheap anti-retroviral drugs, increased aid and the cancellation of debt which enabled better spending in schools and health care systems.
But the economic downturn that has taken away jobs and homes in the developed world threatens lives in Africa.
Prime Minister Brown wants a strong commitment from fellow leaders of the developed world at the G20 summit next month, but many are more concerned about their own economies than the state of Africa.
Few have lived up to the commitments they made to increase aid at the Gleneagles summit in 2005, and some are talking about cutting aid budgets.
There is no agreed figure for what Africa needs, but Mr Kaberuka of the African Development Bank said that the impact was "deeper than anticipated at the beginning".
All of the African leaders in London stressed the need to make finance for trade available again. For now it has completely dried up.
And they all said that the international financial institutions needed to be more flexible.
For Ethiopia, Prime Minister Zenawi talked of a need for better "ease of access", and South Africa's Finance Minister Trevor Manuel said that far more flexibility from the IMF and the World Bank was needed.
"You can't take a cookie-cutter [one size fits all] approach to getting countries out of crisis... we are asking for a lot more speed of action."
Britain has recently been putting public pressure on the World Bank to streamline its processes to ease the availability of funds.