IN THE latest and largest of a string of controversial acquittals, an Indonesian timber baron has walked away from illegal logging charges, prompting an outcry from environmentalists.

The release of Adelin Lis undermines moves by Indonesia for the United Nations climate change conference in Bali to back a multi-billion-dollar program to prevent deforestation.

Because of logging, land clearing and forest degradation, Indonesia is the world's third-biggest contributor to greenhouse gas emissions. It wants the Bali meeting in December to endorse Indonesia piloting the new program to become part of a renegotiated Kyoto Protocol.

The Forestry Minister, Malam Kaban, who this week urged governments and international organisations to support the program, had tried to intervene in the police investigation into Mr Lis.

A letter from Mr Kaban presented at Mr Lis's trial claimed his companies' logging activities were not a crime but "a mere administrative violation".

Police have seized millions of logs cut illegally in Sumatra, but Mr Kaban has complained the operations are harming the province's large pulp and paper industry.

Mr Lis was on the run from police investigators for six months before being arrested attempting to renew a visa at the Indonesian embassy in Beijing last year. At the time, a government statement described Mr Lis as an "environmental destroyer".

Companies connected to Mr Lis allegedly logged timber worth more than $30 billion outside concession areas in Sumatra between 1998 and 2005. Prosecutors requested he receive a 10-year jail sentence.

Environmental groups issued a joint statement condemning the acquittal and demanding an investigation. "The judges have been bribed," it alleged.

The chief judge, Arwin Birin, rejected corruption charges on a technicality, saying they were not valid because Mr Lis's private company had not used state funds. He dismissed illegal logging charges because the companies held forest concession permits.

The firms are among dozens of plantation and timber companies accused of illegal logging across North Sumatra. Earlier this year, the North Sumatra police chief, Nurudin Usman, said he was puzzled by court acquittals of numerous illegal logging suspects. He said he feared Mr Lis would also be freed. Prosecutors said they would appeal against the Medan District Court decision in the Supreme Court.

Widespread corruption is acknowledged as contributing to massive illegal logging.

Mr Kaban presided over a national workshop this week - funded by Australia and the World Bank - to produce a forest protection plan as part of new Kyoto Protocol negotiations in Bali. He said illegal logging should be curbed to help counter climate change. He also warned that the timber industry should not be hampered.

The workshop is fine-tuning plans for Indonesia to pilot the multi-billion-dollar international program to protect forests, in a significant expansion of the Kyoto Protocol. Indonesia will host the December conference to design a successor to the protocol, which expires in 2012. Environmental groups, while endorsing the forest protection plan, question whether Indonesia has the will and capacity to enforce it by cracking down on powerful timber interests.