Google won unconditional approval from the European Commission on Tuesday to buy rival Web advertiser DoubleClick for $3.1 billion, despite objections from rivals and privacy advocates.
Google has already won approval from United States antitrust authorities.
"The Commission's in-depth market investigation found that Google and DoubleClick were not exerting major competitive constraints on each other's activities and could, therefore, not be considered as competitors at the moment," the Commission, the executive arm of the European Union, said in a statement.
Google has by far the strongest position in Web searching in Europe, and the acquisition drew opposition from competitors such as Microsoft and Yahoo .
The Commission also said the combination would lack the power to marginalize Google's competitors in "ad serving," which uses software to help advertisers target potential customers. At the same time, it helps advertisers sell blank space on their Websites.
Ad serving funnels the advertising of its clients down the chain to one of several ad networks, such as Google's AdSense, which work directly with Web sites.
The Commission said that despite the concerns of competitors, the transaction would not close off access to rivals because of such alternatives as Microsoft, Yahoo and AOL.
Privacy advocates complained that the deal would allow the two companies to combine their different methods of gathering information about the habits of Web surfers.