Chantal Bernier, Canada's interim privacy commissioner, says she is concerned by the government's proposal to allow Canada Revenue Agency officials to voluntarily hand over taxpayer information to police if they have reason to believe such information is evidence of a crime.

In her testimony before the House finance committee on Wednesday, Bernier urged the committee to properly demonstrate that information sharing between auditors and law enforcement is needed.

"That is exceptional and therefore should be buttressed by an empirical demonstration of necessity," she said.

The proposal, which is tucked away in the government's hefty 375-page omnibus budget bill, is an amendment to the Income Tax Act that would give auditors the right to disclose information found through the course of their regular duties to police.

The disclosures wouldn't require a warrant or court approval. The taxpayers whose information is disclosed wouldn't even have to be notified.

The proposed amendment also significantly expands the scope of offences through which Canada Revenue Agency officials could justify disclosing information.

Taxpayer confidentiality 'a sacred trust'

As the Income Tax Act currently stands, officials are not allowed to disclose any information unless there's a criminal investigation underway or any serious circumstances with possible danger of death. In other words, only in rare situations.

But under the government's intended changes, auditors can provide police with information if they believe it's evidence of crimes ranging anywhere from bribing public officials to motor vehicle theft to monetarily benefiting from acts of arson.

Allison Christians, an associate professor at McGill University in Montreal who specializes in tax law, said this is further evidence of an "erosion of confidentiality — of privacy in general — from this administration."

"It is certainly the case that taxpayer confidentiality has been a sacred trust, because we want and expect and need taxpayers to voluntarily comply with the tax system," she said in an interview with CBC News.

Without assurances of privacy, Christians said, that compliance is at risk.

Bernier outlined various tests that the proposed amendments would need to pass to maintain the privacy of Canadians, such as making sure any information shared would actually lead to a public good and that there's no other less intrusive alternative.

In an interview with CBC News, Bernier also said there needs to be a proper oversight mechanism in place, especially in lieu of any requirement to go through the courts.

"Obviously tax data can be relevant to criminal investigations," she said. "But there's a process to disclose and we would like to know why this provision would create an exception to that process."

Directly related to criminal activity

Bernier also raised the issue as to whether tax officials should be those who determine what is done in pursuit of public safety.

"That's certainly a question that the committee should examine," she said.

A spokeswoman for National Revenue Minister Kerry-Lynne Findlay said that under the provision, information would only be provided to police if it directly related to criminal activity.

Rebecca Rogers said there are also criminal investigators within the Canada Revenue Agency who would be able to help auditors make such determinations.

She said police would not be able to compel auditors to get specific information.

"Currently, under the existing rules, CRA officials are not able to report evidence of certain serious crimes to police," Rogers wrote in an email to CBC News.

"This needs to change because there have been occasions when CRA officials, in the course of their ordinary duties (e.g., when examining seized computers or seized records), have uncovered evidence of drug trafficking, terrorism, child pornography and contracts for the commission of murder — and have been unable to pass on this information to law enforcement."