Scared out of his wits by a sicko stalker who’s making his life a nightmare, "American Idol" headliner ADAM LAMBERT just hired private investigators to nail the evil creep, who’s not only hacked e-mail accounts, online blogs and voice mail – he’s even contacted the singer’s friends and attempted to defraud them.

"The stalker, who calls himself ‘Jose,’ acts like he’s totally obsessed with Adam," said an insider. "And what makes this assault on his privacy even scarier is that the guy’s in cahoots with a female accomplice, who’s passing herself off as ‘Lane,’ Adam’s real-life personal assistant.

"When friends reported the crooks had contacted them, Adam freaked! He immediately hired private investigators to track and apprehend the stalker duo."

Adam’s not certain he’s in actual physical danger, but he wants the creeps caught before the situation escalates to deadly levels – a la PAULA ABDUL’s stalker incident.

He’s contacted all his friends, warning them "Jose" and "Lane" have his personal contacts list – and might try to con them into sending things like free movie and premiere passes, party invitations, etc.

Stay tuned.