Three departments that oversee Parliament - with an annual budget of $170 million - will be given a blanket exemption from freedom-of-information laws.

The government claimed an ''anomaly'' had been found last year when Fairfax Media obtained information about former Speaker Peter Slipper's travel, catering and clothing purchases.

The new law has been rushed through the House of Representatives even though the results of an independent review on the issue is expected to be released soon, and the departments involved admit they do not need a blanket exemption.

Despite this week's collapse of the bipartisan deal on extra public funding for political parties, the Coalition backed the FOI law change, which both major parties say simply restores the previous understanding that parliamentary departments are exempt.

But lawyer and FOI expert Peter Timmins said the move flew in the face of openness and questioned why it was done when the review's findings were so close.

''These three agencies receive about $170 million in public money to assist in running the Parliament and provide services to members and senators,'' he said. ''Blanket exemptions are troubling.''

One of the bodies to be shielded from FOI requests is the Department of Parliamentary Services. It handles research and library services, television and radio broadcasting, official transcripts, telecommunications, building maintenance and security and is the landlord for commercial tenants in Parliament House.

The two others, the Department of the Senate and the Department of the House, provide advisory and support services to politicians.

Fairfax Media reported last June that Mr Slipper's new coat and tails cost taxpayers $1248, while his travel bill in his first six months as Speaker was more than $18,000. He had also spent more than $8500 on catering. The report was based on a successful FOI application to the Department of the House.

The then attorney-general, Nicola Roxon, said the release of the details was contrary to the ''long-accepted practice'' that the parliamentary departments were exempt from FOI and commissioned Dr Allan Hawke to look into the issue by April 30.

Supporting the new law when it passed through the lower house without dissent on Wednesday, Coalition MP Bronwyn Bishop said the parliamentary librarian had been placed in a ''very difficult position'' after a ruling that the service was covered by FOI.

But librarian Dianne Heriot said in a submission to the review that a partial exemption, rather than a blanket one, would be preferred ''in the interests of transparency and accountability''.

The three departments also said advice should be exempt but administrative documents

should remain accessible.

Attorney-General Mark Dreyfus' office declined to explain why the FOI bill was pushed through before the review's findings were released, saying the legal changes were drafted by Speaker Anna Burke and Senate President John Hogg.

A spokeswoman for Dr Dreyfus confirmed Dr Hawke had completed his FOI review but was still preparing his report.

The bill's explanatory notes say the change ''protects public order'' by guaranteeing the integrity of departments that need to provide independent advice to MPs.

Greens leader Christine Milne said it was disappointing ''that the old parties are not committed to greater accountability'' and called for the Hawke report to be released before the Senate debate.

Leader of the House Anthony Albanese insisted the new law was ''an interim measure'' in advance of the review's completion.