MOUNTAIN VIEW, California: Web search leader Google is preparing for an anti-trust backlash as rival media and online businesses call for regulators to examine its $3.1 billion (€2.28bn; £1.55bn) deal to buy internet advertising firm DoubleClick.

Google outbid Microsoft and Yahoo to reinforce its position as the web's top ad business. A delighted Tim Armstrong, the company's president of advertising, commented: "This transaction will strengthen our advertising network by expanding our access to publisher inventory and enabling us to serve the needs of a broader set of advertisers and ad agencies."

And therein lies the problem, claims Microsoft, which believes the acquisition will allow Google to corner the market and gain access to substantial information about consumers' online behavior.

Warns svp and general counsel Brad Smith: "This... raises serious competition and privacy concerns. We think this merger deserves close scrutiny from regulatory authorities to ensure a competitive online advertising market."

His fears are echoed by telco AT&T's svp of external and legislative affairs Jim Cicconi: "If Google becomes the dominant force in terms of web advertising and becomes the broker, that would be clear evidence of market power and dominant position."

Media giant Time Warner is also reported to be pressing regulators over the deal.

Google has restricted its comments, saying only: "We are confident that this will pass regulatory review. We do not believe this acquisition is anti-competitive, as it promotes a vibrant, healthy market for online advertising."

Data sourced from and Wall Street Journal Online; additional content by WARC staff