The head of the forest monitor group Global Witness called physical threats to his staff by the prime minister's brother unacceptable Wednesday and appealed to donors and officials to investigate the crimes and high-level corruption stripping Cambodia's forests.

"I can only take that as a direct threat, which I think is completely unacceptable," Simon Taylor, director of Global Witness, said, referring to a comment by Hun Sen's brother, Hun Neang, who is governor of Kampong Cham province.

Hun Neang told the Cambodia Daily on Tuesday that if Global Witness staff came to Cambodia again he would "hit them until their heads are broken," in response to a report the group issued last week.

The report links illegal logging to Hun Sen, his wife, a cousin, the Minister of Agriculture and the director of the Forestry Administration. Government members have denied wrongdoing, and on Sunday the Cambodian government banned the report.

Taylor said Hun Neang's threats were typical, but they highlighted the kind of danger Cambodians near valuable forests continually face.

"These kinds of threats illustrate to my mind very clearly what most Cambodians have to deal with, if they are on the ground and face a situation that is very threatening to their livelihoods," he said. "So I think it's something the donors should wake up and take note and deal with."

The report, "Cambodia's Family Trees," was highly critical of donor countries, which, the group said, contribute more than $600 million in aid each year without using the money's political leverage to stop forest crimes or corruption.

Taylor said the lack of progress made over the years pointed to donor "spinelessness" and fear of tough stances.

"It gets difficult, what happens? They collectively duck," he said. "And so to my mind this document is a real wake-up call. We want to see some serious collective action."

Taylor said Global Witness will next push the donor governments at home to investigate the use of aid money and scrutinize their development goals for Cambodia.