Mr Garrett yesterday announced partial approval of Gunns' controversial $2.2 billion mill.

Four modules dealing with the construction of mill workers' accommodation on the Bell Bay site were satisfied last year.

But three modules addressing the effect of mill effluent on commonwealth marine assets remain to be satisfied.

Those studies won't be ready for at least two years.

"The construction works are considerable and there has been an environmental assessment of those and they've been given the all-clear so Gunns can start the construction," Ms Gillard told Network Seven.

"The environment minister, exercising his legal obligations under the relevant federal law as advised by independent experts, has said he wants more work done on the environmental conditions that will be applied to the mill when it's actually in operation.

"So, we get all the construction done then when the mill is actually working there is a question, particularly about what goes into the ocean and how that moves around the ocean a sort of modelling of where the discharge would get to in the ocean.

"That still needs to be done and Gunns has been asked to do that further work so that the environmental process can be worked through to its full conclusion."

Monday's decision as announced by Mr Garrett brought the Government under fire from environmentalists for failing to kill off the mill, while some in the timber industry are disappointed it didn't get full approval.

"What we want to see here, of course, is the best possible environmental standards," Ms Gillard said.

"We've always said that to Gunns, the proponents of this pulp mill, and they've always said that they themselves wanted to acquit a great environmental standard so that part of the approvals process is still there, more work needs to be done, Minister Garrett made that perfectly clear yesterday. But construction can start."