Justice Department lawyer Daniel Therrien told a House of Commons committee the government's cyberbullying bill should be split in two to allow greater scrutiny of measures that would expand online monitoring.
The Conservatives swiftly dismissed the idea.
Therrien's expression of concern came as the NDP — which has painted him as more of a potential lapdog than a true watchdog — tried to get a clear picture of the nominee's views on the contentious legislation.
Civil libertarians say the cyberbullying bill will erode Internet privacy and make it easier for government to spy on the activities of law-abiding Canadians.
The legislation would make it illegal to distribute "intimate images" without consent and remove barriers to getting such pictures scrubbed from the Internet.
The bill also overhauls the system of production orders and warrants to mesh with today's advanced communications world. In addition, it would give police new tools to track and trace telecommunications to determine their origin or destination.
Therrien said the elements dealing with digital communications should be hived off to ensure an "independent review" of privacy interests when it comes to electronic investigations by authorities.
"Canadians want to know about why police and security agencies require information. They want to hear this in order to have an informed debate as to the viability and need for this type of legislation."
Paloma Aguilar, a spokeswoman for Justice Minister Peter MacKay, said Tuesday the legislation had the judicial checks and balances needed to protect Canadians' privacy.
"There is absolutely no need to split this bill."
The privacy commissioner monitors compliance of government agencies and private companies with federal privacy laws, and handles complaints from the public about alleged violations. The appointment requires the approval of both chambers of Parliament.
The Conservative-dominated Commons committee on access to information, privacy and ethics approved Therrien's nomination, despite objections from the NDP that the hour-long hearing was far too brief. He was later questioned by senators for two hours.
During the sessions, Therrien portrayed himself as someone with a deep understanding of government who could effectively serve as an ombudsman, defender and promoter of privacy rights.
Therrien, who has worked for several federal agencies, most recently worked at Justice as assistant deputy attorney general for public safety, defence and immigration.
"Privacy is a fundamental human right, and my career has been about respect for human rights in the application of various government programs affecting liberty and security," he told MPs.
Therrien co-led negotiations on privacy principles that govern the sharing of information between Canada and the United States under the new perimeter-security pact.
The NDP has said a parliamentary officer should not be auditing policies that he himself developed — especially when they're as controversial as the one concerning the Canada-U.S. security deal.
NDP Leader Tom Mulcair wrote to Prime Minister Stephen Harper last month asking him to reconsider Therrien's appointment.
Therrien told Commons committee members Tuesday he has a passion for human rights and, despite his work on government files, would strive to be impartial.
He also defended federal efforts on the perimeter security deal. "I believe appropriate measures have been taken to protect the privacy of Canadians."
Therrien said he wanted to meet with parties interested in privacy rights in his new role. "I realize that I am not well known outside government."
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