"We are doing as much work as possible to ensure Australia's largest known gas resource is developed in an effective, efficient, responsible and internationally competitive manner," said Colin Beckett, Chevron Australia General Manager for the Gorgon project.

Environmental approval from the national government, coming after four years of tough scrutiny and consultations, means the multi-billion dollar project would have cleared all regulatory hurdles and was a step closer towards a final investment decision.

Three years ago Chevron estimated the Gorgon project, which has certified gas reserves of over 40 trillion cubic feet, would cost around A$11 billion (US$9.9 billion) to develop, though analysts have said the final cost could be almost double that.

Chevron had scrapped a 2006 deadline for approving the project after environmental groups protested against plans for an LNG plant to handle the project's gas on Barrow Island, a nature reserve off Western Australia which is home to a rare species of turtle.