BBC Correspondent in Lima
The number of hectares used to grow coca in Peru rose in 2002 as efforts to eradicate the crop in neighbouring Colombia pushed production south.
According to the United Nations Office on Drugs and Crime, the total area used to grow coca now stands at 46,700 hectares.
The figures come just weeks after thousands of coca farmers marched on Peru's capital to demand an end to the eradication of their plants.
Coca growers have managed to stay one step ahead of the government
Despite eradicating more than 7,000 hectares of coca in 2002, peasants who grow the plant have once again managed to stay one step ahead of the government.
This is the third year running that the UN's figures have shown an increase in the amount of land used to grow coca.
Peru remains the world's second largest producer, and now grows enough of the leaf to manufacture 150,000 kilograms of cocaine.
Only Colombia produces more.
Yet Peru's anti-drugs chief, Nils Ericsson, remains optimistic.
Thanks to a new campaign to help coca farmers replace their illicit crops with viable alternatives such as coffee and palm oil - as well as an increase in interdiction efforts - Mr Ericsson hopes to wipe out a further 8,000 hectares this year.
But he is up against market forces.
Coca farmers can earn up to $6 a kilogram - that is up to five times as much as they will get for a kilogram of coffee.
The UN's Peruvian representative told the BBC the main problem is persuading foreign governments to allow legal Peruvian produce into their markets.
Compared with eradication, he said, this is 1,000 times more important.