Together, Google and DoubleClick will be able to deliver more relevant advertising and improve the effectiveness, measurability and performance of digital media for publishers, advertisers and agencies.
The E.U.'s competition regulator reached its decision after a four-month in-depth investigation of the US$3.1 billion merger, which received the approval of the U.S. Federal Trade Commission in December.
The deal is unlikely to harm consumers in ad serving or online advertising intermediation markets, the Commission said.
A merger of Google and DoubleClick will not hurt competition because the companies are not competitors, the Commission said: Google provides online advertising space on its own sites and, as operator of the AdSense service, an intermediary between publishers and advertisers, while DoubleClick offers ad serving, management and reporting services to publishers, advertisers and agencies.
The Commission also examined the risk of Google tying sales of its services to use of those of DoubleClick, or vice versa, to boost revenue. However, it concluded that Microsoft, Yahoo and AOL present sufficiently strong market alternatives that a merged Google-DoubleClick would be unable to exploit the link in that way.
The Association for Competitive Technology (ACT), a Washington, D.C., lobby group for small and midsize entrepreneurial technology companies, welcomed the Commission's decision.
"It demonstrates both the dynamism of our industry and the need to give companies the flexibility necessary to adapt, compete, and meet the needs of consumers," wrote ACT President Jonathan Zuck.
"The merger will undoubtedly change the competitive landscape of our industry and fuel the evolution of internet advertising," he said.
Microsoft is likely to be the biggest beneficiary of the antitrust authorities' approvals, according to Jeff Chester of the Center for Digital Democracy, one of the lobby groups opposed to the merger.
Microsoft recently offered to buy Yahoo for $44.6 billion. If that deal goes ahead it will almost certainly attract the scrutiny of antitrust regulators, as it unites the two biggest players in online advertising after Google.
"By permitting Google to dramatically grow in clout, regulators will have to likely permit the further growth of a number-two competitor to Google, which will be Microsoft," Chester said.
The result will be the emergence of a global digital duopoly over online advertising, Chester warned.
Tuesday's decision only relates to E.U. merger regulations, the Commission said, and does not alter the merged entity's obligations under E.U. law on the protection of individuals and the protection of privacy related to the processing of personal data.
Antitrust regulators have failed to respond to the growing consolidation of control over online ad delivery and data collection, a failure that will have unfortunate consequences for the Internet's role as a democratic communications medium, said Chester.