A proposed update of the U.S. online privacy rule for children sparked debate at a congressional hearing on Wednesday over whether such protections should extend to teenagers.

The Federal Trade Commission plans to update its Children's Online Privacy Protection Rule that gives parents a say over what information websites and other online providers can collect about children under the age of 13.

Some lawmakers and privacy advocates had hoped to see the FTC address online privacy protections for children aged 13 to 17, but the agency's proposal left the age threshold intact.

Mary Bono Mack, who chairs the House of Representatives commerce subcommittee, said she believed the FTC's proposed revisions hit the sweet spot.

While kids are becoming more tech savvy at younger ages, their judgment and awareness of the dark side of the Internet is not growing at the same pace, said Bono Mack, a Republican from California.

The Children's Online Privacy Protection Act (COPPA) of 1998 requires websites and online service operators to obtain verifiable consent from parents before collecting, using or disclosing personal information of children.

The FTC's new proposal makes clear that privacy protections apply when a child is on a cell phone, playing interactive games online or participating in a virtual world. It further clarifies that the law requires parental consent before behaviorally profiling a child.

New consent mechanisms, such as video-conferencing and electronic scans of signed consent forms, are also being added. The FTC is seeking public comment before finalizing the revised rule.

Bono Mack pushed back on calls to raise the COPPA age threshold -- brought on by the boom of users flocking to Facebook, Twitter and Google+ -- and commended what she called common-sense restraint by the FTC to not stray from the current definition of a child, someone under age 13.

The last thing we want to do is to inhibit technological advancements and stifle growth of the Internet by moving forward in a new policy area without a really good, smart game plan in place, she told the hearing.

Stephen Balkam, chief executive for the Family Online Safety Institute, a group whose board includes executives from Microsoft and Google, agreed. He said raising the age would prompt a substantial increase in children lying about their age, negating protections afforded to younger kids.

Balkam added that such a change also risks infringing on teenagers' first amendment rights to free speech.

The FTC's Mary Koelbel Engle also said older kids are more savvy in finding ways to circumvent protections provided through COPPA.

The Commission is considering the privacy interests of teens in its broader review of privacy generally, said Engle, associate director for the FTC's Division of Advertising Practices.

Others argued that turning 13 by no means improves an individual's judgment, and certain mistakes made as a teenager could have repercussions into adulthood.

Bipartisan legislation introduced earlier in the year by Representatives Edward Markey and Joe Barton extends protections to teenagers.

They need resources they can use that are designed for their age group, not for lawyers who are well-versed in privacy, said Alan Simpson, vice president of policy for Common Sense Media, a public interest group.

Bono Mack told reporters after the hearing that she did not have plans to hold a hearing on the Barton-Markey bill.

She added that while she hoped to move data security legislation forward this year, privacy legislation still required more information gathering.

(Reporting by Jasmin Melvin; Editing by Tim Dobbyn)