Google yesterday took the wraps off its new publisher-side ad platform, combining its ad and search technologies with DoubleClick’s. Today, it has been met with a frosty reception from the European Commission over several competition complaints from rivals.

Google’s combined DoubleClick and Google Ad Manager product is designed to ease the complexity publishers face in serving ads, managing ad network relationships and maximizing revenue from inventory sold directly and through ad nets or exchanges, says Google’s blog.

New features include an open API that lets publishers tie in third-party applications like forecasting and workflow tools, integration with the DoubleClick Ad Exchange and new yield-optimization features.

 But the European Commission is now considering complaints from three online companies regarding Google practices including its search rankings, which could stop the search giant dead in its tracks.

The complaints from UK price comparison site Foundem and French legal search engine ejustice.fr allege that Google’s search algorithm demotes their sites in web search results because they compete with Google.

Microsoft-owned Ciao has also complained to European authorities about Google’s standard terms and conditions, which has led Google to tell some reporters that it believes Microsoft has fuelled the complaint fire.

Google has been plagued by regulatory scrutiny in recent years. Most recently, the US Department of Justice has challenged Google’s settlement with book publishers and authors groups to create an online digital archive. The US Federal Trade Commission is also seeking more information on the competitive impact of its proposed $750 million purchase of mobile advertising company AdMob.

Now, the European Commission has written to Google to find out how its search functions work.

But Google is betting publishers will want the simplicity of a single provider to manage their inventory and provide monetization options through either its AdSense ad network or the DoubleClick exchange.

Google said on its blog, “We see an opportunity to improve ad serving even further by combining Google’s technology and infrastructure with DoubleClick’s display advertising and ad serving experience. Since we acquired DoubleClick in March 2008, our engineering and product teams have been working with online publishers to tackle the obstacles that prevent them from maximizing revenues from their websites.”

Either way you look at it, this is a sign of many more battles to come when it comes to the search giants. But is Google really doing anything wrong? Perhaps its competitors are just jealous…