Google hit a road bump in its proposed acquisition of online banner ad services provider DoubleClick with the European Union’s antitrust regulators deciding to open an in-depth investigation into the deal.

In their initial market investigation, EU officials found the proposed merger would raise competition concerns in the markets for intermediation and ad serving in online advertising.

The EU now has has 90 working days (until April 2, 2008) to take a final decision on whether the proposed transaction would significantly impede effective competition within the European Economic Area.

EU antitrust investigators plan to examine whether without the proposed acquisition, DoubleClick would have grown into an effective competitor of Google in the online ad intermediation market.

They also intend to investigate whether the merger could lead to anti-competitive restrictions for competitors operating in the online advertising, intermediation services and ad serving technology markets and harm consumers.