The international environmental pressure group said it discovered some of the biggest brands in electronics had contaminated rivers and wells with a wide range of hazardous chemicals.

To complete its research entitled "Cutting Edge Contamination: A study of environmental pollution during the manufacture of electronic products", released yesterday, Greenpeace took wastewater samples from four printed circuit board plants in Pathum Thani and Ayutthaya for laboratory tests.

The study found that wastewater discharged from a factory in Pathum Thani contained the highest level of copper among all the sites sampled, with a concentration almost two times the maximum allowable level for industrial effluents in the country.

One groundwater sample taken near a factory in Ayutthaya contained nickel at a level above the World Health Organisation's drinking water guideline value and nearly five times the Thai groundwater quality level for this metal.

The study also documents similar problems in Mexico, the Philippines and China.

"While the electronics industry usually likes to portray itself as a clean industry, the situation in many manufacturing facilities, including those in Thailand, shows a different reality.

"The industry is contributing to the worsening problem of water pollution in the country, and considering the declining supplies of clean water everywhere, this issue can no longer be tolerated," said Kittikhun Kittiaram, toxic campaigner for Greenpeace Southeast Asia.

He called on the government to take serious action as the problems are not covered in regulations on water discharges which, he claimed, are too lax to fully mitigate the environmental impacts of the electronics industry.

"There is no reason why it should not also be at the cutting edge when it comes to clean designs and technologies, substitution of hazardous chemicals, greater worker health protection and the prevention of environmental pollution at source," he said.

Anuphan Ittharat, director of the Pollution Control Department's water quality management division, said he would collect water samples from the same sites that Greenpeace did for lab testing again.

"It doesn't mean we don't trust them, but we have checked wastewater in Pathum Thani and Ayutthaya and found the heavy metal contamination was not excessive," he said.

The department only established that wastewater discharged from factories in the two provinces had levels of BOD-biological oxygen demand below standard, he said.