The Viacom entertainment conglomerate has won a ruling that will force YouTube (owned by Google) to disclose details about every person who has ever watched a video at the site: Google must divulge YouTube log.

The ruling comes as part of Google’s legal battle with Viacom over allegations of copyright infringement.

Digital rights group the Electronic Frontier Foundation (EFF) called the ruling a “set-back to privacy rights”.

The viewing log, which will be handed to Viacom, contains the log-in ID of users, the computer IP address (online identifier) and video clip details. While the legal battle between the two firms is being contested in the US, it is thought the ruling will apply to YouTube users and their viewing habits everywhere.

Viacom, which owns MTV and Paramount Pictures, has alleged that YouTube is guilty of massive copyright infringement.

The UK’s Premier League association is also seeking class action status with Viacom on the issue, alledging YouTube has been used to watch football highlights.