Three dozen Malaysian NGOs on Tuesday denounced the world hydroelectric industry's decision to hold a conference in a Borneo state where dam projects have uprooted forests and native peoples.

The groups, including the Malaysian chapters of Amnesty International and Transparency International, said in a statement the choice of Sarawak state "makes a mockery" of the industry's calls for sustainable development.

The International Hydropower Association's (IHA) four-day biennial congress got under way Tuesday in Kuching, capital of Sarawak.

The state's chief minister of 32 years, Taib Mahmud, has faced mounting accusations of enriching himself, family and cronies through a corrupt stranglehold on the state's economy.

"We call upon the IHA to stop this green-washing attempt on behalf of Taib Mahmud's regime," the statement said.

Taib, 77, has come under fire over rapid timber harvesting and a campaign of dam-building blamed for destroying huge swathes of rainforest and driving native tribes from their ancestral lands.

The groups' statement called these "humanitarian and environmental crimes".

Save Sarawak Rivers, a coalition of local NGOs and tribal groups, earlier announced plans for a "parallel congress" in Kuching and other protests this week.

IHA director Richard Taylor has defended the congress as an opportunity to share sustainable practices.

"The IHA is happy to have the opportunity to interact in this way, and we feel that the current willingness to engage should be acknowledged and encouraged, rather than campaigned against," he said in emailed comments to AFP.

Save Sarawak Rivers has said, however, local stakeholders are excluded by high delegate fees.

Swiss-based forest-protection group Bruno Manser Fund (BMF), citing financial and corporate records, estimated Taib's net worth at $15 billion last year, which would make him Malaysia's richest man.

Taib is regularly cited by anti-graft groups as typifying endemic corruption in Malaysia.

He is accused of handing land and timber concessions and government contracts to companies controlled by himself, his family, and close allies.

He has denied wrongdoing, saying the backward state must be developed. His office has not responded to requests for comment on the congress.

Malaysian anti-corruption authorities have failed to act against Taib, whose political party is vital to keeping the 56-year-old ruling coalition in power.