The EPA said Gorgon’s location on ecologically sensitive Barrow Island could damage the local ecosystem and harm endangered turtles that nest on the island.

But the EPA also recognised the government's decision would be based on consideration of social, economic and strategic issues, as well as environmental matters, and has therefore provided a draft framework under which the project could proceed.

"We are very strong supporters of the project," Carpenter said on Tuesday afternoon. "We would be bitterly disappointed if this project did not go ahead. It's a very big project for Western Australia and it has to be taken into a bigger context."

Omedei made it clear that the opposition Liberal party offered bipartisan support for the project.

Gorgon operator Chevron said the joint venture would continue participating in the environmental assessment process, which will culminate in final approval by the Western state and Federal governments later this year.

Australia’s peak industry association representing the upstream gas industry, the Australian Petroleum Production and Exploration Association (APPEA), welcomed the support given by the two major.

“The Gorgon partners have worked extremely hard to address environmental concerns and have done so diligently, thoroughly and involving the world’s most renowned environmental experts,” APPEA chief executive Belinda Robinson said.

“It also involves the world’s first commercial carbon sequestration project. It’s hard to imagine what more could be done.

“Gas has a major role to play as Australia and the world face the dual challenges of long-term energy security and reducing greenhouse gas emissions.”

Robinson said it was “critically important” that the Australian industry’s international LNG customers retained confidence in Australia’s ability to reliably and consistently supply gas to world markets.

“The Premier observed today that natural gas represents an abundant source of low greenhouse gas emissions energy for Australia’s future,” she said.

“LNG also has massive potential in assisting a world that is struggling with the greenhouse problem. It is a bright light for near-term, cost effective global action and should be strongly and widely supported by all governments and the Australian community.”

Robinson said Australia’s upstream petroleum sector was proud of its track record of first class environmental assessment and protection.

“This nation’s upstream petroleum sector has the skills and experience to operate in sensitive environments. Chevron has won seven international and Australian awards for environmental excellence over the past 40 years – a period in which it has produced 300 million barrels of oil from the Barrow Island fields.

“APPEA looks forward to seeing the appropriate regulatory processes, including any appeals against the EPA’s decision, progress as quickly and efficiently as possible.

“The Gorgon project is a world class gas resource of more than 40 trillion cubic feet, and its development has the potential to deliver 6,000 jobs, $2.5 billion in annual export income, and more than $17 billion in government taxes and royalties over its 60 year life.”

The joint venture responded individually to 1100 questions from the public, environment groups, government agencies and other stakeholders, and enhanced its development and operating proposal to accommodate views expressed during the public consultation process.