Google’s $3.1bn acquisition of online ad firm DoubleClick has led to concern in several quarters, with online rivals concerned that Google will be too dominant in the online ad market.

Now, a US consumer group is attempting to challenge the deal because of concerns over the privacy of internet users.

The Electronic Privacy Information Center (EPIC) has filed a complaint which alleges that Google and DoubleClick don’t take adequate measures to protect the privacy of the personal information on consumers which both companies collect.

According to EPIC, the Google/DoubleClick deal:

“Will give one company access to more information about the Internet activities of consumers than any other company in the world. 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.”

Google unveiled its new Web History service last week – a feature that allows Google account holders to view and search a log of Web pages they’ve visited.

Meanwhile, Martin Sorrell, Chief Executive WPP, the world’s second largest advertising group, has also questioned the deal. He is concerned that the move will give Google too much control over the online ad market.

“I think the DoubleClick acquisition clearly raises some regulatory issues which a number of media owners, publishers and competitors like Microsoft are very exercised about.”

Like EPIC, Sorrell is also concerned about privacy issues:

“It raises issues as to whether we are happy to let Google have our client’s data and our own data which Google could use for its own purposes in contextual and targeted advertising.”

According to Sorrell, some have estimated that the acquisition of DoubleClick will give Google 83% of the contextual and targeted online ad market.