Google has defended its privacy policy following the launch of a service which offers to manage users' medical information online.

Google yesterday launched Google Health, a hosted service which allows users to store and manage information regarding their health online, and share that information with nominated individuals.

Privacy campaigners were quick to criticise the service. Deborah Peel, founder of PatientPrivacyRights.org, argued that the risks of such a system were "massive".

Jeff Chester, executive director of the Center for Digital Democracy, claimed Google would scan users' documents for the purposes of serving targeted adverts. "There is no question in my mind that, at the end of the day, this is about marketing pharmacology and health-related products to consumers," he told press agency AFP.

Google immediately sought to quash such concerns. Speaking to SCMagazine today, a company spokesperson said that users had total control of who can access their records, and that they were able to revoke access at any time.

"We let users know what information we collect, how we use it and how we keep it safe. We will not sell a user's health information or share it with others unless the user explicitly authorises us to do so," the spokesperson said. "It's important to note that a limited number of employees at Google have access to confidential information of any sort. Only the people who are operating and improving Google Health have access to user information, and they are bound by strict policies not to disclose this information to others."

The company added that its Health platform is kept secure by "SSL encryption, firewalls and alarms".

Google has "no plans to run ads at this moment in time", the spokesperson added, saying that Google Health would only be available in the US "for the forseeable future".

Microsoft has a rival product called HealthVault, which has attracted similar privacy concerns.

Meanwhile, at a Google conference, the company's co-founders have warned that the internet industry is harming itself over the way some companies treat privacy issues.

Without naming specific cases, Sergey Brin said some firms were pursuing commercial objectives in a "creepy and scary" way.

While defending the value of user information for improving search results, Brin said: "Some companies have aggressively pursued a very commercial orientation in a creepy, scary way. That's an issue which is a setback for the industry."

Brin's co-founder Larry Page said Google had little choice but to tread carefully and to build trust with users, according to the Financial Times.