SAN FRANCISCO -- The Federal Trade Commission on Thursday fined Google $22.5 million to settle charges that it bypassed privacy settings in Apple's Safari browser to be able to track users of the browser and show them advertisements, and violated an earlier privacy settlement with the agency.
The fine is the largest civil penalty ever levied by the commission, which has been cracking down on tech companies for privacy violations and is also investigating Google for antitrust violations.
"The social contract has to be that if you're going to hold on to people's most private data, you have to do a better job of honoring your privacy commitments," said David C. Vladeck, director of the commission's Bureau of Consumer Protection, in a call with reporters. "And if there's a message the commission is trying to send today, it's that."
The commission said Google broke the terms of a 2011 settlement over privacy missteps related to the now-defunct Buzz, a social networking tool. In the settlement Thursday, Google did not admit to violating the law.
One commissioner, J. Thomas Rosch, filed a dissenting statement because he said the commission should not have accepted Google's denial of liability, which he called "inexplicable."
Google has said its actions were unintentional and had resulted from a change in Safari of which Google was unaware. When the issue was brought to the company's attention, it said, it stopped tracking Safari users and showing them personalized ads.
On the call with reporters, Mr. Vladeck said he had little patience for Google's explanation and referred to other privacy violations about which Google has also said it was unaware, such as collecting personal data with its Street View cars.
"As a regulator, it is hard to know which answer is worse -- 'I didn't know,' or 'I did it deliberately,' " Mr. Vladeck said. "We hope that the civil penalty we're imposing here today and continued monitoring of Google's performance by the commission and by others, frankly, will force Google to have a better sense of what's going on."
Some analysts have questioned the commission's power to effectively police tech companies, which have repeatedly settled privacy violations with the commission. The fine, although large by commission standards, is small for Google.
An investigation by ProPublica, published in Wired magazine in June, said federal regulators do not have enough financing or legal authority to sufficiently monitor and punish tech companies for privacy violations.
Safari, unlike other browsers, blocks cookies from ad networks such as Google's. But Google had been exploiting a loophole to avoid the block, install cookies and track Safari users to show them personalized ads.
In a statement, Google said, "We set the highest standards of privacy and security for our users." The company added that it had "taken steps to remove the ad cookies, which collected no personal information, from Apple's browsers."