Gmail users have no "reasonable expectation" that their e-mails are confidential, Google has said in a US court filing.
Consumer Watchdog, the advocacy group that uncovered the filing, called the revelation a "stunning admission". It comes as Google and its peers are under pressure to explain their role in the National Security Agency's mass surveillance of US citizens and foreign nationals.
"Google has finally admitted they don't respect privacy," said John Simpson, Consumer Watchdog's privacy project director. "People should take them at their word; if you care about your e-mail correspondents' privacy, don't use Gmail."
Google set out its case last month in a bid to dismiss a class-action lawsuit accusing the tech giant of breaking wiretap laws when it scans e-mails to target advertisements to Gmail users.
That suit, filed in May, claims Google "unlawfully opens up, reads, and acquires the content of people's private e-mail messages". It quotes Eric Schmidt, Google's executive chairman: "Google policy is to get right up to the creepy line and not cross it."
"Unbeknown to millions of people, on a daily basis and for years, Google has systematically and intentionally crossed the 'creepy line' to read private e-mail messages containing information you don't want anyone to know, and to acquire, collect, or mine valuable information from that mail," the suit claims.
In its motion to dismiss the case, Google said the plaintiffs were making "an attempt to criminalise ordinary business practices" that have been part of Gmail's service since its introduction. Google said "all users of e-mail must necessarily expect that their e-mails will be subject to automated processing". Google said, "Just as a sender of a letter to a business colleague cannot be surprised that the recipient's assistant opens the letter, people who use web-based e-mail today cannot be surprised if their communications are processed by the recipient's provider in the course of delivery."
Simpson said: "Google's brief uses a wrong-headed analogy; sending an e-mail is like giving a letter to the post office. I expect the post office to deliver the letter based on the address … I don't expect the postman to open my letter and read it.
"Similarly, when I send an e-mail, I expect it to be delivered to the intended recipient with a Gmail account based on the email address; why would I expect its content will be intercepted by Google and read?"