The G8 must act to halt spiralling rises in food and oil prices and to increase aid to developing nations.

This was the message from the Secretary General of the United Nations, Ban Ki-moon and World Bank President, Robert Zoellick.

"The world faces three simultaneous crises," said the UN Secretary General, "a food crisis, the fuel crisis and a development crisis.

"The Millennium Development Goals can address development. The G8 must agree to deliver on its commitments. No new promises are needed."

His comments came as debate among the G8 leaders continued on aid to the developing world. At the Gleneagles Summit in 2005 the G8 agreed to increase aid by $50 billion a year by 2010, half of which would go to Africa.

But, with just two years to go, the G8 countries are falling short of meeting their commitments. Some estimates claim that they are as much as $30 billion short of the aid target.

"For rich countries, $50 billion is pennies, for Africa this is life and death," said Oxfam's Max Lawson.

Mr Ban also obliquely criticised the G8 leaders for not going far enough on the current crises. "Our efforts so far have been too sporadic, divided and too little," he said. "The time has come to take a very different approach. The UN stands ready to help."

Aid agencies also spent the first day of the summit calling on the G8 leaders to meet their promises. These include commitments on climate change that would see carbon emissions cut by 50% by 2050, and providing universal access to treatment for HIV by 2010.

Tearfund's Peter Grant said, "The framework was set out in Gleneagles and now is the time to deliver on those promises.

"The money pledged is even more urgently needed now because of the current food and fuel crises," he added.

However, criticism has also been levied at African leaders meeting their G8 counterparts in Japan today.

In a meeting earlier today, it was reported that some African leaders criticised the idea of sanctions against Zimbabwe. They apparently told the G8 leaders that "Mr Mugabe would retire in a few years time", and that sanctions could cause "internal conflict".

This move was condemned by Christian aid agency Tearfund. "This is a missed opportunity", said the agency's Peter Grant. "It's unacceptable that ordinary people in Zimbabwe should continue to suffer and die because the regional and global leaders are not willing to act."