The federal government has given timber company Gunns until January next year to complete an environmental impact management plan for its controversial pulp mill in northern Tasmania.
The plan - due to be submitted by October 4 - is only a quarter complete.
The mill was given the go-ahead, subject to 48 approval conditions, last year by the previous Howard government.
Environment minister Peter Garrett says Gunns had sought an extension to the October 4 deadline.
After "careful and thorough consideration" he had agreed to extend the deadline to January 5, 2009.
The plan required a "thorough and rigorous examination" of the issues surrounding the proposed mill.
"It is not unusual for major projects to need additional time to ensure that all environmental matters are fully investigated and properly addressed," Mr Garrett said in a statement.
The comprehensive assessment of every aspect of the Gunns plan must not be rushed, he said.