Google Inc. said in court documents unsealed Thursday that Viacom Inc. was secretly uploading videos to YouTube at the same time it was complaining about copyright infringement.

Google also said that Viacom tried to buy YouTube in 2006 before the search giant agreed to pay $1.65 billion for the popular video Web site.

The documents are part of the $1 billion copyright-infringement suit brought by Viacom against Google in March 2007.

In a blog post Thursday, YouTube Chief Counsel Zahavah Levine wrote, "For years, Viacom continuously and secretly uploaded its content to YouTube, even while publicly complaining about its presence there. It hired no fewer than 18 different marketing agencies to upload its content to the site. It deliberately ‘roughed up' the videos to make them look stolen or leaked. It opened YouTube accounts using phony email addresses. It even sent employees to Kinko's to upload clips from computers that couldn't be traced to Viacom."

Google's charges of hypocrisy were matched by similar claims by Viacom.

Viacom said Google executives did little to curb illegal downloading on YouTube even though they were aware of the large amount of videos illegally uploaded to the site.

"Google and YouTube were not just innocent and unwitting accomplices to infringement perpetrated by YouTube users," Viacom said in the court documents.