The drilling project could lead to a massive offshore gas extraction project, with reserves in the area valued at $50 billion.

Advent Energy, through its subsidiary company Asset Energy, plans to begin exploratory drilling for natural gas 27 kilometres to 55 kilometres off Newcastle.

There are fears that drilling will affect migratory and threatened species, including whales, marine turtles, sharks, birds and fish.

Concerns have been raised that government process for the plan lacks transparency.

Primary Industries Minister Steve Whan said many state and federal agencies would assess Advent's environment plan for the project.

"It is not a statutory requirement for the environment plan to be made public," Mr Whan said.

He said federal legislation dictated that a "summary environment plan" was to be made public 10 days after the full environment plan was "assessed and accepted by government".

Community environment network chairman John Asquith described the process as unbelievable.

A member of Mr Asquith's group is on a community consultative committee, which Mr Whan set up to "ensure ongoing liaison with stakeholders".

Mr Asquith said the committee was biased and "full of spin".

His group was told by the committee it would receive a copy of the environment plan, but that had not occurred.

Advent has repeatedly claimed it would begin drilling, which is expected to take up to 30 days, in October, but Mr Whan said it was not expected to start before November. He said a consultative committee meeting was planned for October 15.

Mr Whan said the consultative committee would "meet regularly during the exploration phase of the project to provide information and consult on community concerns".

It would be the first time exploratory drilling had occurred off the NSW coast.

Mr Whan said state and federal governments jointly regulate offshore exploration under Commonwealth legislation.

Gaining government approvals to extract gas will be at least four years away.