The simmering romantic rivalry between blonde bombshells Heather Locklear and Pamela Anderson has reached the boiling point again. Fanning the flames is Pam’s budding romance with comic David Spade, whom Heather was dating last year.

“Pam has always been Heather’s nemesis,�? a friend of Heather tells Star. “On a professional level, she has no respect for her. And on a personal level? Forget it!�?

Even though Heather, 45, has been seeing her former Melrose Place costar, Jack Wagner, for the past few months, she “flipped out�? when she saw photos of David rubbing Pam’s bare midriff during a recent hookup in Las Vegas, says sources. And she really lost it when she saw another shot of them kissing at the JET nightclub in the Mirage Hotel. “Heather went ballistic,�? says the friend. “When she split with her first husband, Tommy Lee, Heather told him he was free to go after anyone but Pam. Tommy not only married Pam, he had two children with her!�?

Heather filed for divorce from her second husband, Bon Jovi guitarist Richie Sambora, in February 2006, and a month later, she was linked to Spade, 42. When they broke up, Heather was “miserable,�? says the friend. And she was jealous of the other women he dated, including Carmen Electra.

But as with Tommy, she had specifically asked Spade to steer clear of Pam- even though she seemingly had little reason to worry.

When Heather and Spade vacationed in Hawaii last year, her friend notes, the funnyman- who turns 43 on July 22- even took potshots at 40-year-old Pam!

“Heather was laughing at his jokes about Pam’s intelligence,�? says the pal.

“David’s barbs were very sharp. That’s why Heather was so astounded to see him hooking up with her. Now Heather is furious. She says she can’t believe what a lying hypocrite David is. And if she runs into him, she says she’ll tell him straight to his face!�?