Tasmania's Lower House has passed legislation giving the timber company Gunns more time to begin substantial work on its planned pulp mill.

The government used its numbers to gag debate on the Pulp Mill Clarification Bill after four hours of fiery exchanges.

The legislation extends the mill's construction permits to August 2011.

The Greens leader, Nick McKim, repeatedly called on the Government to release its legal advice on the matter.

"Don't give me the line that you never release Solicitor-General's advice, you do," he said.

The Primary Industries Minister David Llewellyn said the reason behind the amendment was clear.

"The purpose of this bill is to clarify what the intent of the original assessment act was."

The Greens say the government's use of the guillotine smacks of the tradition established under the former Premier, Paul Lennon, who always put the mill before the interests of Tasmanians.