Liberal MP Jamie Briggs wants the federal government to explain why cabinet may have considered Treasury costings of Greens policies.

The shadow parliamentary secretary has been on a freedom of information crusade to have Treasury release about 14 policy costings for the minor party.

Freedom of Information Commissioner James Popple reportedly has asked the department to provide him with the documents deemed exempt from release so that he can consider himself whether they were part of cabinet deliberations.

Mr Briggs said the government was not being totally honest about where its budget measures came from.

"How possibly could it be that a Greens costings request could be going to cabinet?" he told Sky News on Wednesday.

"It's about time the Australian people knew what the little secret was that the Labor Party's so desperately trying to hide."

Australian Greens leader Christine Milne tried to turn the issue back on the opposition, saying at least her party had released some of the costings Treasury did, whereas the coalition has not detailed how much any of its policies will cost.

"They won't submit their proposals to Treasury because they say they (the costings) may be released ... , which is precisely what they're trying to force here," she told ABC radio.

Mr Briggs said the coalition would release a full range of costings before the election.