Federal Environment Minister Tony Burke has accused the New South Wales Government of leaking confidential information to improve the election chances of the Federal Opposition.
In a letter sent to the NSW Government before Christmas, Mr Burke flagged his intention to approve Whitehaven's Maules Creek open-cut coal mine, near Boggabri.
The letter was leaked by NSW Resources Minister Chris Hartcher, who is now accusing Mr Burke of delaying the mine's approval for political gain in the lead up to the federal election.
The mine is one of three in the Leard State Forest that will together form a mega mine complex, which will clear at least 5,000 hectares of land and produce 23 million tonnes of coal annually.
Mr Burke's assessment of the project under the Environmental Protection and Biodiversity Conservation Act - the final hurdle in the approval process - was due on February 7, but he deferred his decision until the end of April.
He says leaking the letter was an extraordinary move.
"For the New South Wales Government to take an extraordinary step like they have, misrepresent the situation, effectively lie to the people about the situation, and then in doing so, breach the publication of commercially sensitive information, is an extraordinary thing," he said.
"Barry O'Farrell needs to decide if he is running a government or a PR machine." Mr Burke says will no longer send confidential information to the NSW Government.
"Because they contain commercially sensitive information, no state government up until today has ever breached that confidence," he said.
"This is probably the last time I'll be able to responsibly share any of that information with [New South Wales], but that's a call they've made."