The federal government has been keeping almost a year's worth of pollution data secret, despite it being scheduled for release in May, documents obtained under freedom of information laws reveal.

Independent estimates suggest Australia's greenhouse gas emissions have risen sharply since the government last released its quarterly data in December - a trend that would make the nation's commitment to cutting emissions more disruptive and expensive.

Quarterly updates by the National Greenhouse Gas Inventory, described as "up-to-date information on emissions trends for business, policymakers and the public", have been released 28 times since 2009, but not since last year.

Documents obtained under FOI by the Australian Conservation Foundation reveal that while the government possesses data on greenhouse pollution for the two quarters leading up to the end of last year, it has failed to release them.