Oil giant Shell's proposal to drill for oil and gas just 50km from Ningaloo Marine Park poses a threat to Ningaloo Reef and WA's richest fisheries, according to the company's own studies.
Modelling data show that a spill comparable with the 2009 Montara disaster off the Kimberley could swamp the reef and pollute the ocean as far south as Perth.
Environmentalists have reacted angrily to Shell's proposal for the Palta-1 exploration well near the reef, which the Federal Government has nominated for United Nations World Heritage status.
Shell spokesman John Dagostino said the firm was committed to protecting biodiversity and had "a very high standard of operating practices".
But documents submitted to the Federal Government show a Montara-type event could create a plume of hydrocarbons spreading north and west of Exmouth and as far south as Rottnest and Perth.
The projection, produced on Shell's behalf by consulting firm Asia-Pacific ASA, is based on a spill in which thousands of barrels of condensate a day are released from the sea bed for 77 days - similar to the Montara incident - and in which winds and tides spread the residue south.
Such a spill off Ningaloo would have grave consequences for the region's valuable fisheries, as well as for the reef, its whale sharks and migrating whales, WWF's WA director Paul Gamblin said.
The proposed drilling area is inhabited by endangered species, including loggerhead and leatherback turtles, blue whales and southern right whales.
Federal Resources Minister Martin Ferguson said Shell would face "stringent processes" to get approval for its plan and that the Government was working to learn the lessons of the Montara and Gulf of Mexico oil spills.
But Mr Gamblin said it would be premature for the Government to approve the drilling before its Montara inquiry was complete.
Acting Premier Kim Hames insisted the State Government would have final say on the project.
He said the Government was "very concerned" about protecting Ningaloo Reef and that it had not yet received details of Shell's plans.
WA Greens MP Robin Chapple urged the Barnett Government to kill off the proposal.
"While I am not surprised that Shell has the nerve to propose drilling near an environmental jewel like Ningaloo, I expect the State Government to warn Shell off this proposal from the start," he said.
See video of WWF's response at