ANTI-pulp mill protesters are gathering outside the Tasmanian electorate office of Labor MP Jodie Campbell.

A spokesman for The Wilderness Society, Vica Bailey, said scores of protesters were about to converge on Ms Campbell's Launceston office to deliver their verdict on the federal government's decision to approve construction of Gunns Ltd's Tamar Valley pulp mill.

Environment Minister Peter Garrett approved the mill's construction on Monday and all but approved its operating conditions, pending some further testing.

Mr Bailey said The Wilderness Society was part of coalition of anti-pulp mill groups converging on Ms Campbell's office at midday on Tuesday.

"Community members will today take their concerns over Mr Garrett's part approval of the pulp mill to the electorate office of Jodie Campbell and deliver their verdict on the decision," he said.

"In addition to the approvals, the protest will focus on the two-year extension granted to Gunns to carry out hydro-dynamic modelling, work that should have already been completed.

"This extension represents a second deadline missed and potentially opens up avenues of legal challenge.

"It leaves Tamar residents and Tasmania as a whole with their lives in the balance, waiting on a final outcome for Gunns environmentally destructive pulp mill."