More than 300 people have rallied on the lawns of Parliament House to protest against an amendment to the pulp mill assessment Bill.
Long-time anti pulp mill campaigner Peter Cundall said the pulp mill assessment process had been "the most colossal and cynical swindle" in Tasmania's history.
Mr Cundall has been arrested for protesting against the pulp mill on the steps of parliament in the past.
"We have got to stop meeting like this," he said.
Wilderness Society campaign manager Vica Bayley, who convened the rally, said the legislation was "injustice heaped upon injustice."
"It has brought down a Premier, it has brought down a deputy premier... It has brought down it's biggest champion of all, which was it's proponent, Gunns," Mr Bayley said.
Greens Leader Nick McKim joined the rally after parliament broke for lunch at 1pm.
McKim said his attempt to move a no-confidence motion against the government for the legislation in the House of Assembly had been ignored by the parliament.
"They have colluded to prevent us even tabling our no-confidence motion in the parliament today," he said.