The European Commission has confirmed it is looking into complaints by three European search companies, although it has said it has “not opened a formal investigation for the time being.” Google pointed out soon after the news broke that one of the three companies—Ciao—was a Microsoft subsidiary, while another, Foundem, is a member of an advocacy group that has been funded by Microsoft.

In his response, Heiner says that Microsoft is indeed “concerned about Google business practices that tend to lock in publishers and advertisers and make it harder for Microsoft to gain search volume” and adds that as part of the European Commission’s review of the Microsoft-Yahoo (NSDQ: YHOO) search partnership, Microsoft did tell the European Commission about Google behavior that “may be harming publishers, advertisers and competition in search and online advertising.”

In a sign that Microsoft isn’t at all interested in being polite, Heiner’s response also takes aim at Google CEO Eric Schmidt, noting that when Schmidt led Novell that company “was never hesitant about complaining to regulators about Microsoft.” Ouch.

Google isn’t commenting.