Lula told the meeting at the UN's Food and Agriculture Organisation (FAO) headquarters in Rome that access to food was "a right, a sacred right, a fundamental right", adding: "Hunger is the best weapon of mass destruction which exists today.
"It's killing men, women and innocent children, even before they have a chance to cry and say 'I'm hungry'!" said Lula to applause from delegates from more than 100 countries attending the event.
Lula was earlier awarded the Agricola Medal by FAO, the UN body's highest award, for what FAO Secretary-General Jacques Diouf said were his tireless efforts to create "a world free from hunger and want".
The Brazilian president was one of nine heads of state to address the conference, as was Zimbabwe's President Robert Mugabe, who has flouted a European Union travel ban in order to attend, despite protests from US and Italian officials.
Mugabe, 81, defended his controversial Land Reform programme - which has seen more than 5000 white farmers thrown off their land - as not only "an empowerment programme ... redressing past gross imbalances in land ownership, which were institutionalised by British colonialism, but is also the provision of a wealth-creating resource".
"As a result of our Land Reform Programme, my government has been allocating substantial budgetary resources to agriculture, directed at the provision of crop and input support, tillage, mechanisation and dam construction."
Robert Mugabe: Land reform
redresses past imbalances
Mugabe added that agriculture subsidies in developed countries "has had a crippling effect on the development of agriculture in developing countries".
Hunger is political
Venezuelan President Hugo Chavez said hunger was a political problem of "gargantuan proportions", and criticised developed nations for their lack of commitment to solve it.
"The FAO gets $900 million a year, not even one billion. Compare that to what developed countries devote to their agricultural production: One billion a day.
President Hugo Chavez: Hunger a
gargantuan political problem
"In one day they are investing in subsidies what FAO can allocate in one year," said Chavez.
"In Washington, they have just announced their defence budget for the coming year: $500 billion. That's enough to finance FAO for 500 years!"
In his speech, Diouf warned that FAO must adapt to the changes of the past 60 years "if it is to rise to new challenges and profit from emerging opportunities".
He said he was seeking the approval of member states to implement a programme that would enable FAO "to play an increasing effective role in hunger eradication, in the development of sustainable agriculture, in food safety".