New Democratic Party Leader Dominic Cardy is urging the federal Liberal government to make a decision quickly about the proposed Sisson mine project in New Brunswick.

A new study by the Canadian Environmental Assessment Agency found not enough has been done to offset the "significant" impact the 12.5 sq.-km mine would have on four Maliseet communities that have traditionally used the area northwest of Fredericton for hunting, fishing and gathering resources.

The chiefs of five First Nations and the chief of the Wolastoq Grand Council have all called for the Sisson mine proposal to be rejected by the federal government.

An environmental assessment process is taking place and a decision is expected this summer.

Cardy said a quick decision is needed to bring clarity to the situation.

"I really hope that the federal Liberal government moves quickly so that we can have clarity here in New Brunswick on the influence of our First Nations communities over projects like this," said Cardy.

'Do they have a legal veto or not?' - Dominic Cardy, NDP leader

"Do they have a legal veto or not? At the moment it's not clear and it makes it really hard for any outside investors who want to set up shop in New Brunswick."

The Sisson Partnership issued a statement Thursday saying "it will continue to engage the Maliseet First Nations in a meaningful and constructive manner."

Woodstock First Nation did not join the other five First Nations in calling for the mine to be rejected. Chief Tim Paul declined to comment.

The proposed open pit tungsten and molybdenum mine would mine 30,000 dry tonnes a day for 27 years. The proponents put the cost of the mine at $579 million and say it would create 500 jobs during construction and 300 during its operation.

The site would also include one of the world's largest tailings ponds to hold waste from the mining operation.

David Coon

Green Party Leader David Coon is concerned the "giant tailings pond" at the proposed Sisson mine could contaminate the Nashwaak River watershed. (CBC)

The comprehensive study concluded the mine can be developed and operated in an environmentally responsible manner.

Green Party Leader David Coon said the opposition to the mine by the Maliseet "is not surprising at all."

"There are huge issues around Aboriginal title and Aboriginal rights that were largely being ignored and not being addressed," said Coon.

The Green MLA for Fredericton South said Aboriginal people aren't the only ones with concern about the proposed mine.

"The acceptability of that risk posed by that giant tailings pond for many people living in the region, Aboriginal or not, didn't meet the straight-face test," said Coon.

With files from Catherine Harrop