Google's recent DoubleClick deal has raised the eyebrows of European Union regulators, who say they believe the search giant may be breaking the law by retaining user data for as long as two years, according to a Bloomberg.com report.

Google's privacy counsel in Paris, Peter Fleischer, confirmed that the company had received a letter from EU regulators asking to explain why the company retained user data for so long.

According to Greg Sterling, an analyst for Sterling Market Intelligence, the issue of data retention impacts the entire online ad industry.

Fleischer said Google was committed to working with regulators to improve privacy practices.

Recently Google said it changed its data storage policy, retaining information for not more than two years.

In the U.S., the New York State Consumer Protection Board has urged federal regulators to delay approval of Google's DoubleClick acquisition until the company can give users the right to prevent tracking and storing of data.

EU regulators also are looking at privacy policies at Microsoft and Yahoo! to ensure compliance.