"The recommendations for more liberalisation would lead to more violations of the right to food," she said in a statement.
Since the 1996 world food summit, "we have warned continually that the current model would lead to a food crisis, and it has."
The farmers' groups criticised multi-national food corporations whose profits have shot up through the crisis.
Flavio Valente, a Brazilian activist, said it was "about time we treated this as a crime against humanity".
Dena Hoff, an American activist said: "In the first quarter of 2008, profits of Monsanto have already shot up by 108 per cent, while Cargill registered profit increases of 86 per cent... More food aid would help these companies, but do not offer any solutions for the poor and hungry."
However, the UN and some food agencies hailed the summit a success.
"The most important thing about the summit is that it has focused attention on the world leaders and on something that has been ignored for too long," Matthew Wyatt, from the International funds for agricultural development, said.
"We've let investment in agriculture drift terribly. In 1979 it was 18 per cent of all aid. Now it's less than 3 per cent, that's absolutely ridiculous... We have to reverse that.
"If there is a good and strong declaration particularly with the commitment to small-holder farming and commitments to boosting supplies, that would be a bonus," Wyatt said.
Ban Ki-Moon, the UN secretary-general, said: "I think these kinds of conferences are important to put together people discussing. I think it's more important outside the big room and the official speeches.
"It's important to know each other because many times we meet in the operation and if we know each other we can work better together," said Massimo Barra, a Red Cross representative.
The summit is due to issue a declaration later on Thursday committing to eliminating hunger and ensuring food supply sufficiency.
However, according to Mark Seddon, Al Jazeera's correspondent in Rome, the delegates are struggling to agree on a final declaration.
Seddon said: "This has taken a lot longer than anyone expected. There's a consensus that this was a good event to have in that it has concentrated the eyes of the world on the problem.
"However, in terms of concrete deals, it has not been a great success."