Experience has shown that "Google will keep making attempts to delay investigations through continuous correspondence and always freshly packaged arguments," Peter Schaar, Germany's federal data protection commissioner, said in a report on Wednesday. Facebook was separately described earlier this month as having "impertinent" behaviour by Thilo Weichert, the privacy regulator for the German state of Schleswig- Holstein.
Google and Facebook are among US internet companies that have faced scrutiny in the European Union for possible privacy-rule violations over the use of consumers' personal data.
Google, operator of the world's largest search engine, faces investigations after it changed its privacy system to create a uniform set of policies for more than 60 products last year. Six data protection regulators started "coordinated" enforcement measures this month over the company's failure to fix complaints about the new system.
Al Verney, a spokesman for Google in Brussels, did not respond to a call and e-mail seeking comment. An e-mail to Google's German press office also was not immediately returned.
Facebook, which has its European base in Ireland, was subject to an audit by the Irish data-protection authority into privacy issues with its facial-recognition feature last year. That review pushed the owner of the biggest social-networking site to delete data identifying faces in users' photos.
Germany's Mr Weichert said in a statement on April 19 that it's "brash how Facebook is trying to take those who are politically responsible for fools" as it sought to increase traffic to its site and find "political and social acceptance."
A German appeals court yesterday rejected a bid by Weichert's agency to force Facebook to allow users to register under pseudonyms. The Menlo Park, California-based company said the court recognised that Facebook's European operations are supervised by the Irish data protection regulator.
"We're seeking to have a constructive dialogue with all groups, also with our greatest critics," Facebook said in a statement. "Dialogue means: one shouldn't just talk about Facebook, but also with Facebook."
Microsoft's recent changes to its service agreement are also being examined by EU regulators.
"It's a similar investigation to the one with Google," Mr Schaar said in his report, which summarises the German regulator's activities in 2011 and 2012.
* Bloomberg News