Jacques Diouf, the head of the UN food agency, says he is not satisfied with the final declaration of the UN World Summit on Food Security in Rome.
The final declaration, made on the first day of the three-day meeting, pledged "urgent action" to boost food security, but did not include exact targets.
Diouf, head of the UN Food and Agriculture Organisation (UNFAO) said that he was not present when the statement was decided, and criticised the lack of a deadline for the total eradication of world hunger.
The UN estimates more than one billion people worldwide - one in every six people - are going hungry.
Diouf said: "I thought it made sense to set that target, and I thought we would be discussing whether it should be in four years or five years or so on, not that we would be eliminating any target date in the declaration."
"I am not satisfied that some of the concrete proposals I made were not accepted. There was no consensus on this and I regret it."
The summit also rejected a call by the UN to commit £26bn per year to develop agriculture in developing countries. The UN warns that if more land is not used for food production, 370 million people could face famine by 2050.
Oxfam supported Diouf's comments, calling the summit's declaration "uncosted, unfunded, and unaccountable".
The summit comes a year after huge rises in food prices caused chaos in many developing nations.
Critics have questioned how effective it would be, as most of the leaders of the world's richest nations are not attending. Silvio Berlusconi, Italian prime minister, is the only leader from one of the G8 leading industrialised countries to take part.
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