Commissioner Vasant Panich said 11 of 31 samples tested on July 14 and 17 were contaminated with GM seeds in the eastern province of Rayong and the northeastern provinces of Mahasarakham, Chaiyaphum and Kalasin.

The first contamination was found last year in the northeastern province of Khon Kaen, after the environmentalist group Greenpeace accused the government of illegally selling genetically-modified papaya seeds from a research station there.

Farmers in the four provinces surveyed in July said they had received the papaya seeds from the same research station.

Greenpeace filed a complaint with the rights commission, alleging the contamination violated the rights of farmers and consumers, damaged the environment and breached a 2001 law that banned field trials of genetically-modified organisms, known as GMOs.

Vasant urged the government to destroy the contaminated fields, to compensate farmers for their losses and tighten laws banning GMO field trials.

'We need a biosafety or consumer protection law before we start open field trials,' he said.

The Human Rights Commission only has advisory powers.

The cabinet banned GMO field trials in 2001. The current law forbids the public sale of GMO seeds and requires products containing more than 5 pct of a genetically-modified ingredient to be clearly labelled.