Mr. Radwanski said the bill would give the state broad authority to force an invasive procedure on law-abiding people, with little promise it would be effective and no proof it addresses a large-scale problem.

"This proposed bill would violate privacy in the most profound way possible because it would take away that right to control access not only to the most sensitive private information about ourselves, but even to our physical selves as well," he told the Commons justice committee.

The bill, introduced by Tory-DRC MP Chuck Strahl and backed in initial votes by a majority in the Commons, is designed to let emergency workers such as paramedics and police know whether they have been infected by viruses like hepatitis or HIV when they deal with suspects or accident victims.

Many AIDS workers and civil-rights advocates oppose the bill.

However, organizations representing police officers and health-care workers are in favour of it. They cite the case of Ottawa police Constable Isobel Anderson, who was jabbed with a bloody syringe as she searched the pockets of an armed-robbery suspect.

Worried about HIV infection, she began treatments with a drug cocktail that causes serious side effects but can prevent the virus from taking hold. But she stopped the drugs in part because the robber tested negative for HIV.

Mr. Radwanski told the committee that protecting health-care workers is laudable, but the bill's provisions would be an ineffective and unwarranted reduction of rights.

He said that a negative test does not guarantee there's no HIV infection, for example, because the virus might not be detected for several months after a person is infected.

He also said there has been only one confirmed case in Canada, and two possible cases, of someone being infected with HIV on the job, so it is not clear that the problem is big enough to warrant a large reduction in rights.

When Mr. Strahl raised the possibility that police officers could be assaulted with needles or bitten, Mr. Radwanski said he would be less concerned if the bill applied only to assault suspects, rather than accident victims.

"Maybe you surrender an element of your right to privacy when you bite someone," he said. "I'm not sure you surrender it when you collapse bleeding on a sidewalk."

Mr. Strahl's Tory-DRC coalition and the Canadian Alliance said they believe the balance of rights should favour people who fear they have been infected, and might choose to take toxic drugs.