Social networking site Facebook, online retailer eBay and search company Yahoo are supporting the video-sharing site YouTube in its case against media conglomerate Viacom. The technology companies filed a friend-of-the-court brief in a Manhattan court on Wednesday.

The companies said if Viacom wins, it would hamper the development of the internet and e-commerce.

The media conglomerate had slapped a $1bn copyright lawsuit on YouTube in 2007. It alleged that the video-sharing site encouraged users to upload unauthorised clips from production houses such as Paramount Pictures, Comedy Central and MTV Networks to the site.

Viacom has argued that although users posted copyrighted videos to YouTube, the site's founders retained the videos to attract more users before they sold the business to Google.

The three internet companies urged the court to dismiss Viacom's suit saying the Digital Millennium Copyright Act shields internet service providers from liability for copyright violations by users.