Police have charged two people with trespass and were expecting to charge a third person on summons after they allegedly chained themselves to machinery at the Malaysian-owned company's Smithton mill yesterday morning.

Construction, Forestry, Mining and Energy Union forestry president Jane Calvert said the "extremist protests" could scuttle the last-ditch efforts to salvage a deal from the talks.

"Ongoing informal talks have been entered into in a spirit of goodwill," Ms Calvert said.

"Unfortunately acts such as these are extremely unhelpful and risk derailing the process.

"Most of us want to reach agreement, but we are being hampered by behaviour that ignores workplace safety."

Tasmanian Forest Contractors Association chief executive officer Ed Vincent said the "work-site invasions" were dangerous.

"This threatening turn of events places any potential for a forestry agreement at greater risk and is counter to the objectives of the industry, the community and even the vast majority of environmentalists," Mr Vincent said.

Ta Ann is already considering the future of its Tasmanian operations after formal talks between groups involved in the forestry peace negotiations broke down at the end of last month.

Yesterday the company expressed disappointment about the protests and urged the groups to reach agreement as soon as possible.

The Wilderness Society and Environment Tasmania are considering an offer of a compromise deal from the Forest Industries Association of Tasmania. The Examiner's calls to the groups for comment yesterday were unsuccessful.