A coalition of Thai conservation and community groups is planning to sue its government over the controversial Xayaburi dam in Laos.

Conservationists allege Thai firm Ch.Karnchang has begun building the dam at the behest of Thailand and in violation of international obligations to secure agreement from affected downstream countries.

In addition to violating a 1995 agreement between the four lower Mekong countries – Cambodia, Thailand, Laos and Vietnam – to study downstream impacts before building a dam, the groups alleged the Thai government has breached its own constitution.

Teerapong Pomun from Living Group Siam said the coalition would sue the government and the Electricity Generating Authority of Thailand (EGAT), which has a power-purchasing agreement with Laos, on August 7.

“The first thing that the Thai government failed to do by the Thai constitution was to give the information to the public before doing any activity that will impact environmental health and the community,” he said.

EGAT did not respond to inquiries yesterday, while Ministry of Natural Resources and Environment officials did not comment.

Laos claims the project will not go ahead until downstream impacts are studied.

Thai Foreign Ministry spokesman Thani Thongpakdee said he was not aware of details of a lawsuit but welcomed assurances from Laos that further environmental impact studies were being commissioned.

“We have always stressed the importance about conducting this project in a transparent manner,” he said.

Meanwhile, Pöyry, the company behind a much-criticised study into the project, said yesterday an arm of its company the World Bank has placed on a list of “non-responsible vendors” is not linked to Xayaburi.

“This matter and respective subsidiary company have nothing whatsoever to do with [Xayaburi],” spokeswoman Anne Viitala said.

To contact the reporter on this story: David Boyle at [email protected]