Lachey, who has recently been linked romantically to former beauty queen LIZZIE ARNOLD, has now been spotted in the arms of CACEE COBB, according to US magazine Life + Style.
In its new issue, the publication claims the couple was spotted getting cosy at Los Angeles' Level 3 nightclub last week (29JAN06) as onlookers gasped in astonishment.
One reveller says, "Nick had his arms wrapped around her, and he was kissing her all over the side of her face and neck. Her arms were around him, too.
"We were watching in total disbelief. We kept waiting for them to rip each other's clothes off."
The revellers felt Cobb should not have been cavorting with her best friend's ex in such a public place.
One fumes, "There may be nothing going on between them, but it was inappropriate behaviour. Everyone was like, "Wow, what are they thinking?"
But Lachey's representatives are strongly denying rumours of a romance between their client and Cobb, insisting, "Nick and CaCee are friends, that's it."