Environmentalists warned Wednesday that planned power lines on Malaysia's Borneo would threaten the island's tribsespeople, urging the Asian Development Bank to shelve a $45 million loan to export electricity from controversial dams.

The proposed loan would be used to build cross-border transmission lines from Sarawak state -- where protests against dam building have increased in recent years -- to West Kalimantan on Borneo's Indonesian side.

Peter Kallang, head of NGO Save Rivers said the ADB loan did not constitute a "win" for the state's local people.

"The rivers that are planned to be dammed by Sarawak Energy to generate this electricity are our lifeblood. Investing in this company to build transmission lines means becoming complicit in destruction," he said in a statement.

Some 40 environmental and human rights group had on Monday in a letter warned ADB that there was "reputational and financial risks" against the lines associated with the loan to dam-building firm Sarawak Energy.

Officials in the Malaysian state of Sarawak have for years been accused of ramming through controversial dams while natives in the state have staged increasingly frequent demonstrations and road blockades in recent years over the dams.

Thomas Jalong of Jaringan Orang Asal SeMalaysia also urged ADB not to approve the cross border power trade loan.

"It is the Indigenous Peoples -- the Kayan, Kenyah, Penan, Iban, Kajang and Bidayuh -- whose customary lands and livelihoods are at stake in this equation," he said.

Malaysia's biggest dam, Sarawak's Bakun hydroelectric facility, has been called a "monument to corruption" by Transparency International, displacing more than 10,000 people, many now living in squalid resettlements.

Four dams in the state -- at Bakun, Murum, Baleh and Baram -- are expected to put out nearly 6,000 megawatts of power, six times what Sarawak currently uses.

Sarawak's longtime former chief minister Taib Mahmud, who is now governor of the state, has faced mounting accusations of enriching himself and cronies through a stranglehold on the state's economy, charges which he denies.