The advice was sought after Opposition Leader Tony Abbott pledged to repeal the carbon price, and following the introduction of the legislation into Parliament in September, The Australian Financial Review reports.

Under the legislation, carbon units are defined as "personal property", prompting claims that Labor had planted a "poison pill" to ensure a future Coalition government would be forced to pay compensation to companies that had bought forward permits.

Climate Change Minister Greg Combet also warned the Coalition would have to explain how it would compensate companies if the legislation was repealed.

But his department has refused to release the advice, claiming it was a long-standing practice that such opinions were "generally not disclosed as doing so may prejudice the Commonwealth's legal interests".

However, the Gillard government has previously released legal advice: when the High Court stymied the Malaysia refugee swap deal and in relation to the Water Act and draft guide for the Murray-Darling basin.

As a result, the opposition called yesterday for the carbon advice to also be released. "This government has been more than happy to release legal advice when it suits them," shadow environment parliamentary secretary Simon Birmingham said ­yesterday.