YouTube has announced that it is cracking down on "sexually suggestive" videos in a bid to clean up the popular video-sharing website.

In a blog posting, YouTube, which already bans pornography, said it would be enforcing a "stricter standard for mature content" and "tightening the standard for what is considered 'sexually suggestive'".

"Videos with sexually suggestive (but not prohibited) content will be age-restricted, which means they'll be available only to viewers who are 18 or older," the Google-owned website said.

"Our goal is to help ensure that you're viewing content that's relevant to you, and not inadvertently coming across content that isn't."

YouTube said videos which contain sexually suggestive content or profanity would no longer appear on its lists of "Most Viewed" or "Top Favorited" videos.

The internet's top video-sharing site also said it would step up enforcement of rules banning misleading descriptions in the tags and titles of a video.

In addition, thumbnails will be will now be algorithmically (ie randomly) selected in order to cut down users who manipulate frames within their videos in order to get a provocative thumbnail to appear with their video listing.

Some YouTube users have been known to give videos misleading titles such as "sexy" in a bid to increase the view counts of a particular video.

YouTube, which receives 13 hours of video from users every minute, said repeat violaters of the new rules will have their accounts terminated.