A California state senator on Monday said she was drafting legislation to block Google Inc.'s free e-mail service "Gmail" because it would place advertising in personal messages after searching them for key words.

"We think it's an absolute invasion of privacy. It's like having a massive billboard in the middle of your home," Sen. Liz Figueroa, a Democrat from Fremont, California, told Reuters in a telephone interview.

"We are asking them to rethink the whole product," she said.

In late March, the world's No. 1 Web search company announced plans to launch Gmail -- a service that would offer users 1 gigabyte of free storage, more than 100 times the storage offered by other free services from Yahoo Inc. and Microsoft Corp.

But in return for the extra storage, users would agree to let Google's technology scan their incoming e-mail, then deliver targeted ads based on key words in the messages. For instance, a user receiving a message about a friend's flu symptoms might also receive ads for cold and flu remedies.

Gmail is now being tested with a limited number of users. Privacy advocates are assailing Gmail even before its formal launch. Google faces heavy opposition in Europe, where privacy laws are stricter than they are in the United States.

European groups recently lodged a complaint with UK authorities, charging that Gmail may violate Europe's privacy laws because it stores messages where users cannot permanently delete them. Europe's privacy protection laws give consumers the right to retain control over their communications.

Google said in a statement that it intends to work with "data protection authorities across Europe to ensure their concerns are heard and resolved."

Industry analysts see the service as a key product for Google because it would boost revenues from advertisers and expand its business as the Mountain View, California-based company nears an expected initial public offering of stock.

Figueroa, who was the author of California's "Do-Not-Call" law that allows citizens to block telemarketing calls, said she was pursuing the legislation because she had not yet received a response to an April 8 letter to Google co-founders Sergey Brin and Larry Page, in which she laid out her concerns.

"We received the letter from Senator Figueroa. We appreciate her feedback and will take it into consideration as we build the best possible webmail service for our users," Google said in an e-mailed statement.

FREE STORAGE ENTICEMENT

The Gmail service would bring Google into into the market for free e-mail services now dominated by Yahoo Inc. and Microsoft Corp.'s  MSN. Those rivals have been challenging Google's core Web search business.

More than two dozen privacy groups in the United States and Europe have demanded that Google suspend Gmail's launch until privacy issues are adequately addressed.

The groups charged, among other things, that scanning e-mail for ad placement poses unnecessary risks of misuse and that the system sets "potentially dangerous precedents and establishes reduced expectations of privacy" in e-mails.

"We are confident that Gmail is fully compliant with data protection laws worldwide," Google said in a statement.

"Google has the highest regard for the privacy of our users' information. We have taken great care to architect Gmail to protect user privacy and to deliver an innovative and useful service," said Google, which added that it is actively soliciting user feedback on its privacy policies.