Crude oil and gas have been flowing into the Timor Sea for more than a fortnight.
The Federal Government says the slick is now between 25 and 70 nautical miles in area.
A rig which is being sent to the site to drill a relief well to stem the flow of oil is expected to arrive Thursday.
Environment Minister Peter Garrett says the process will not be subject to some of the environmental approvals normally required.
"Last night I formally exempted these actions from the requirements from the EBPC Act on the basis that it was in the national interest to do so," he said.
The Minister for Resources and Energy, Martin Ferguson, says it will then take about a month to stop the leak.
Published by Mike Hitchen i On Global Trends, world news, analysis, opinion
Putting principles before profits
Environment Pollution West Atlas
Putting principles before profits
Environment Pollution West Atlas