Google's merger with advertising technology firm DoubleClick will now go ahead after the European Commission cleared the deal.
The $3.1 billion (£1.5bn) takeover can now go ahead, as it has also been cleared by US regulators.
After an in-depth investigation, opened in November 2007, the commission concluded the transaction would be unlikely to have harmful effects on consumers, either in ad serving or in intermediation in online advertising markets.
In a statement, the commission said: "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."
Microsoft complained the deal would be anticompetitive, saying it would give the search engine provider too much power in online advertising.
DoubleClick mainly sells ad serving, management and reporting technology worldwide to website publishers and to advertisers and agencies.
The company's technology allows internet publishers and advertisers to ensure that advertisements are posted on the relevant websites and to report on the performance of such advertisements.
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