Social networking site, Facebook, has faced sharp criticism from the European data protection officials for putting users privacy at risk due to the changes it brought to its service, a media report said.

The Financial Times stated in a report that,"Officials advising European Commission said in a letter to the social networking company that changes to its default settings in December were 'unacceptable'."

It is the strongest rebuke yet for the US company from European data protection officials and indicates an increasing willingness to crack down on privacy violations, the report added.

Officials have said that Facebook needed default settings that ensured only selected contacts could see user profiles and users should be able to choose explicitly whether their information could be accessed by search engines.

In December, Facebook had made changes wherein, users profiles were made accessible to others by default and certain aspects' such as lists of friends' were impossible to keep private.

FT cited Facebook's director of public policy in Europe, Richard Allen, as saying that he was considering the company's response to the letter.

Facebook has made a few adjustments to address privacy concerns raised by European regulators in the past, but Allen has said there could be some areas where the company would be unwilling to compromise.

The latest letter to Facebook is from Article 29 Working Party, an influential group of data protection officials from 31 countries, which advises the European Commission on privacy matters.