OTTAWA — Opponents of the government's online surveillance bill say Canada should look to its allies for cautionary tales before pushing ahead with measures that would erode Internet freedom.

Experiences in other jurisdictions such as the United States and Britain show no evidence of improved crime-fighting ability and "overwhelming evidence of increased surveillance," said Micheal Vonn of the British Columbia Civil Liberties Association.

The Canadian legislation would allow police, intelligence and competition bureau officers access to Internet subscriber information -- including name, address, telephone number, email address and Internet Protocol address -- without a warrant. An IP address is the numeric label assigned to a computer on the Internet.

It would also require telecommunication service providers to have the technical capability to enable police and spies to intercept messages and conversations.

The government says its proposed legislation is consistent with that of the United States, Britain, Australia and New Zealand.

The international examples demonstrate that when authorities are given more powers to keep an eye on Internet surfers, they definitely use them, said Vonn.

"If you build it, they will come," she said.

The government insists the bill will improve Canada's ability to work with its international partners to fight crime and terrorism.

But critics question the rationale for the legislation altogether, saying no one has made a strong case that the current system -- based on voluntary compliance and warrants -- isn't working well.

"We're not seeing a very strong need for these bills, and we're seeing an expansion of surveillance powers that basically begs for abuse," said Lindsey Pinto, a spokeswoman for OpenMedia.ca, which has helped lead opposition to the measures.

Some warn that legislation without strong oversight and other protections will invite problems of the kind seen abroad.

Inappropriate access to the sort of transactional data -- not the content, but all of a message's identifiers -- that Canadian authorities seek under the bill is a "common problem" in both Britain and the United States, says a research paper by Christopher Parsons, a University of Victoria doctoral student who has studied the issue.

"In the U.S. the problem is far more significant," he writes. "The U.S. suffers from endemic inappropriate surveillance."

The U.S. National Security Agency eavesdropping service ran a warrantless wiretapping system with the assistance of major telecommunications providers, while the FBI has repeatedly strayed over the line when collecting information, he notes.

The American experience shows law enforcement agencies tend to access communications data inappropriately when there is unclear -- or no --judicial oversight, he adds.

Research in Britain indicates people have been placed under surveillance for minor infractions such as littering and smoking in a public place.

The Canadian government cites safeguards in its bill, including record-keeping requirements and regular internal audits to ensure the powers aren't abused.

But it's not yet clear how they would work.

"We do need to make sure that there is clear oversight and really meaningful deterrence from abuse," said Pinto.

Being slower than its key allies to implement such legislation, Canada is in the ideal position take a different approach, said Vonn.

"As usual we're being told we're way behind and we have to do exactly the same thing."