Plans by Google to offer free email to take on rivals such as Yahoo Mail and Microsoft's Hotmail have been thrown into confusion by a Californian senator who is plotting legislation that could force the company to drop the idea.

Democratic senator Liz Figueroa believes Google's plans to pay for the service by scanning customer's emails in order to send them tailored advertisements, is a breach of privacy. She is considering legislation to stop Google from launching its Gmail service in its present form.

Ms Figueroa wrote to the search engine company about the plan a week ago saying the proposal puts the "priorities of advertisers above the interests and desires of individuals".

"Quite simply, there is no hue and cry among emailers to have ads put into their emails - just as there is little or no interest among phone users to hear, at the beginning of a call, 'this conversation is brought to you by'," she said. "I cannot urge you strongly enough to abandon this misbegotten idea."

Google's plans for Gmail, announced on April 1, have caused consternation among privacy advocates and lawyers on both sides of the Atlantic.

On April 6, an international coalition of US privacy and civil liberties organisations including the Electronic Privacy Information Centre and the Consumer Federation of America sent Google a letter asking the company to suspend the service until privacy concerns could be more thoroughly addressed.

In Britain a spokeswoman for the information commissioner confirmed yesterday that the data protection watchdog has received a complaint about Gmail from campaigners Privacy International. However, no action has yet been taken.

She added that Google is receiving compliance advice from the watchdog, which insists that consumers give their "informed consent" to the way in which their personal data is handled. Google said in a statement yesterday that it is confident Gmail is "fully compliant with data protection laws worldwide".