Microsoft launched an ardent attack against Google late last week, accusing the web giant of anti-competitive behaviour.
The software vendor's deputy general counsel Dave Heiner wrote a missive on Microsoft's corporate blog on Friday, in which he highlighted complaints levelled at what he sees as Google's questionable business practices.
"Our concerns relate only to Google practices that tend to lock in business partners and content - like Google Books - and exclude competitors, thereby undermining competition more broadly," grumbled Heiner.
His comments came at the end of what had been a torturous time for Mountain View, with its increasingly strained relationships with various regulators and companies in Europe underlined last week.
Microsoft-owned outfit, Ciao!, and two other small online businesses filed a complaint with European Commission watchdogs last Wednesday.
The EC, which is the legislative body of the European Union, confirmed it was investigating Google to see if it has broken competition and anti-trust laws, although no there is official inquiry yet.
A UK price comparison site called Foundem, a French legal search engine ejustice.fr and Microsoft have all complained that Google tweaked search results unfairly to push them further down the rankings than they should be.
"As Google's power has grown in recent years, we've increasingly heard complaints from a range of firms - large and small - about a wide variety of Google business practices," wrote Heiner.
"Some of the complaints just reflect aggressive business stances taken by Google. Some reflect the secrecy with which Google operates in many areas. Some appear to raise serious antitrust issues."
Google has said it will cooperate with the probe and hand over information to the Commission.
"We are confident that our business operates in the interests of users and partners, as well as in line with European competition law," it said. The search giant also took to its own corporate blog to dismiss the complaints as an inevitable result of its success.
Elsewhere, Microsoft has taken its fight against Google to the US Department of Justice over the search kingpin's plans to digitise millions of books.
"Ultimately the competition law agencies will have to decide whether or not Google's practices should be seen as illegal," griped Heiner.
Of course, some might view Microsoft's aggressive stance against Google as an attempt to redirect regulators' attention onto Mountain View.
Microsoft has battled with antitrust watchdogs for years over complaints that its exploited its effective operating system monopoly into other markets.
Heiner grumbled that Google's deals with advertisers and publishers was keeping Microsoft's efforts to compete with its search engine, in the form of Bing, at bay. He urged companies that felt they had been hurt by Google's dominance in search to take their complaints to "competition law agencies". ®