Google has been told to improve its privacy policies or face enforcement action by the UK data watchdog.
The Information Commissioner's Office (ICO) said the US multinational's updated privacy policy has raised "serious questions" about its compliance with the UK Data Protection Act.
The warning came after similar announcements were made by several other data protection authorities, including in France and Spain.
An ICO spokesman said: "We have today written to Google to confirm our findings relating to the update of the company's privacy policy. In our letter we confirm that its updated privacy policy raises serious questions about its compliance with the UK Data Protection Act.
"In particular, we believe that the updated policy does not provide sufficient information to enable UK users of Google's services to understand how their data will be used across all of the company's products.
"Google must now amend their privacy policy to make it more informative for individual service users.
"Failure to take the necessary action to improve the policies compliance with the Data Protection Act by September 20 will leave the company open to the possibility of formal enforcement action."
The move comes after the ICO ordered Google to destroy four discs containing information it unlawfully took from unsecured wifi networks using its Street View cars.
The ICO warned Google that failure to comply with the legal order would be considered contempt of court.
Google said it was immediately proceeding with plans to delete the data.
A group of EU data protection authorities recently wrote to Google seeking information about its new Google Glass device and how the company intends to ensure compliance with data protection laws.
And France's privacy watchdog, the Commission Nationale de l'Informatique et des Libertes, ordered the company to comply with a series of specific privacy requirements within three months or face fines.
