OTTAWA -- The federal information commissioner says the Conservative government is setting a "perilous precedent" by retroactively rewriting Canada's access-to-information law to absolve the RCMP of wrongdoing.

Suzanne Legault says if the government is allowed to retroactively change the law, there's nothing preventing parliamentarians from rewriting election laws to stop cheaters from being prosecuted.

A special report tabled in Parliament on Thursday reveals Legault recommended almost two months ago that charges be laid against the RCMP for its role in withholding and destroying gun registry data.

But instead of Justice Minister Peter MacKay moving on the recommendation to lay charges, the Harper government rewrote the law, backdated the changes and buried the amendment in an omnibus budget bill last week.

Legault said the issue goes far beyond the now-defunct gun registry.

"We could do the same thing after investigating potential electoral fraud. We could erase these things retroactively," she said in an interview.

Or the former Liberal government, she said, could have stripped auditor general Sheila Fraser of her investigative power at the height of the sponsorship scandal.

"This is the kind of precedent that we are proposing to set with these proposed amendments. Now that is why this matter is very serious," said Legault.

She said each member of Parliament "is going to have to look themselves in the mirror and decide whether they can, in their own integrity, actually vote in favour of those proposed amendments."

Legault filed a suit Thursday in Federal Court in an effort to preserve the rights of the complainant in the case, who had been seeking copies of the now-defunct, long-gun registry.

In a letter to the Speakers of both the House of Commons and the Senate, Legault said she was submitting her special report "in the hopes that parliamentarians will carefully consider the implications of Bill C-59," the omnibus budget implementation bill.

The RCMP responded to the report by stating it felt it had fully complied with provisions of the Access to Information Act.

"The RCMP would vigorously defend against any accusation of unlawful conduct in respect of the handling of this Access to Information request," spokesman Sgt. Harold Pfleiderer said in an email.

Under the provisions in Bill C-59, the Mounties won't have to defend anything.

The omnibus budget bill exempts any "request, complaint, investigation, application, judicial review, appeal or other proceeding under the Access to Information Act or the Privacy Act," related to those old records.

Legault revealed that this is the fourth time she has recommended to the attorney general of Canada that there are grounds for criminal charges under the Access to Information Act.

No charges have ever been laid, despite past findings of blatant and illegal political interference in the workings of the system designed to inform Canadians about the activities of their government.

Prime Minister Stephen Harper said the Mounties were just obeying the will of his Conservative majority government.

"The government, the Parliament of Canada, has already decided to abolish the long-gun registry," Harper said at an event in Windsor, Ont. "The RCMP have acted fully within Parliament's intention in destroying the data in the long gun registry."

Harper asserted that the dispute is over contradictions between the Access to Information Act and his government's legislation to end the long gun registry. That is not the case.

In fact, the dispute revolves around the RCMP refusing to disclose gun registry data while the Conservative bill was still being debated and not yet law.

Nonetheless, the Conservative move will be popular with gun advocates.

The complainant in the case had been seeking a complete list of the long-gun registry data -- with names and other personal identifiers redacted under the Privacy Act.

Legault found that when the RCMP eventually delivered the more than eight million files, it had deleted some categories of information that should have been provided under the Access to Information Act.