A federal government decision on the three remaining modules of the $2.3 billion project's environmental impact management plan was due yesterday but Environment Minister Tony Burke extended the deadline until Thursday.

Mr Burke said Gunns representatives contacted his department on Wednesday indicating the company wanted tougher environmental controls than those in the original application.

However, Gunns said it had been talking to the department about the measures for some time.

In other developments yesterday:

•Rebel Greens MHA Kim Booth warned he would campaign to bring down the Labor-Greens state government if it gave further financial support to the pulp mill project.

•In the face of environmental groups' campaign for the introduction of a high- conservation forest logging moratorium this month, a key industry body warned such a step could take 12 months to implement.

Mr Burke said Gunns had sought to have the tougher controls included with the other decisions he had to make on environmental impact management.

"My department needs to assess these proposed variations to the original pulp mill proposal and allow the independent expert group to examine these variations," he said.

In a statement to the Australian Securities Exchange, Gunns said the more stringent environmental aspects had been proposed after consultation with the community and environmental non- government organisations.

"We want to ensure we build this pulp mill using the best available technology, with the best environmental controls available," managing director Greg L'Estrange said.

"We are pleased that minister Burke and his department are willing to give further consideration to these enhancements."

A Gunns spokesman denied the company had waited until the day before the decision was due to contact the department.

He said the company had been talking to the department for some time in relation to the measures.

He would not detail what the measures were or which groups it had consulted.

The Wilderness Society, the Australian Conservation Foundation and Environment Tasmania welcomed the delay to Mr Burke's decision.

"The current proposal for the pulp mill, put forward by Gunns in 2007, would cause unacceptable damage to the environment, so it is appropriate that the minister give the company longer to improve its proposal," The Wilderness Society's campaign director, Lyndon Schneiders, said.