"I am not satisfied with the fact that there is no commitment regarding the calendar, amounts and conditions," Diouf said.
In particular, Dioouf said he regretted the "absence of a deadline for the total eradication of hunger in the world", referring to the UN Millennium Development Goal deadline of 2025.
Pope Benedict XVI, the Roman Catholic pontiff, criticised the "greed which causes speculation to rear its head even in the marketing of cereals, as if food were to be treated just like any other commodity".
Matt Grainger of Oxfam was among many activists who criticised the outcome, calling it "completely uncosted, unfunded and unaccountable".
|The leaders of Libya and Italy attended but not the leaders of the wealthiest nations [AFP]
"They really had a chance here to come up with something really concrete," Grainger told the AFP news agency, calling the summit a "massive wasted opportunity".
Some 60 heads of state and government were attending the World Summit on Food Security, but leaders of most of the world's wealthiest countries were absent.
Monday's declaration outlined five "principles" including "direct action" to help the most vulnerable.
But no new financial commitments were contained in the document, which calls on wealthy nations to honour pledges of $20bn in aid over the next three years made at a Group of Eight summit in July.
Opening the summit, Ban Ki-moon, the UN secretary general, said "the food crisis of today is a wake-up call for tomorrow".
By the time the world population reaches some nine billion in 2050, "we know we will need to grow 70 per cent more food, yet weather is becoming more extreme and more unpredictable", he said.
The UN chief added that the issues of climate change and food security are interlinked.