A consumer group asked the Federal Trade Commission Friday to investigate and block Google Inc.'s proposed $3.1 billion purchase of online advertising firm DoubleClick Inc. unless the companies improve consumer privacy protections.

The complaint, filed by the Electronic Privacy Information Center (EPIC), alleges that Google and New York-based DoubleClick collect exhaustive personal information on consumers using the Internet but don't adequately protect the privacy of that information.

Google's acquisition of privately held DoubleClick ''will give one company access to more information about the Internet activities of consumers than any other company in the world,'' the complaint from the Washington-based group said. ''There is simply no consumer privacy issue more pressing for the Commission to consider than Google's plan to combine the search histories and Web site visit records of Internet users.''

The complaint cites published reports that claim Google plans to combine its data with DoubleClick's and can track an individual's Internet searches and Web site visits.

DoubleClick said Google would not have access to the data it collects on consumers who view its online ads. That data belongs to clients, DoubleClick said in a prepared statement out Friday.

A Google spokesman was not able to immediately comment on the complaint.

On Thursday, Google unveiled Web History, a feature that allows Google account holders to view and search a log of Web pages they've visited.

EPIC's complaint said that each Google user has a unique, trackable Internet ''address'' and that Google keeps a record of user searches.

The complaint also charges that Google doesn't disclose this on its ''privacy policy highlights'' Web site page. Users must ''click'' through four separate Web site pages before the information is disclosed.

Google said in March that it would remove identifying features from user search data after 18 to 24 months. EPIC's complaint, however, noted that earlier this year, data from Time Warner Inc.'s AOL division was linkable to individual users even though the company said identifying features had been erased.

The FTC investigated DoubleClick, whose ads reach up to 85 percent of Internet users, was in 2000 after EPIC filed a complaint about its information collection practices. The FTC closed its investigation when the company agreed to several reforms, including a pledge to abide by privacy standards of the Network Advertising Initiative, a consortium of online advertising companies.

The Center for Digital Democracy and the U.S. Public Interest Research Group joined EPIC's latest complaint, which asks the FTC to order Mountain View, Calif.-based Google to improve privacy practices before the merger can be approved. The requested improvements include instituting a ''meaningful data destruction policy'' and allowing consumers access to data the company has about them.

An FTC spokesman confirmed that the agency has received EPIC's latest complaint, but wouldn't comment on whether it would initiate an investigation.

The FTC investigates allegations of unfair or deceptive business practices, and along with the Justice Department, reviews proposed mergers and acquisitions to address antitrust concerns.