THERE’s a new wrinkle in the relation­ship between Jennifer Aniston and Courteney Cox – the former “Friends” co-stars are feuding over Botox!

Jen, 45, has come out publicly as NOT being a fan of the injectable beauty booster while Courteney, who turns 50 on June 15, has been looking like she can’t get enough of it.

As The ENQUIRER recently reported, Courteney has been trying to find a way to turn back the clock ever since she started dating 37-year-old Irish rocker Johnny McDaid of Snow Patrol. She once called Botox “fantastic” and admitted that she’s “game for anything” when it comes to halting the aging process in its tracks.

Meanwhile, Jen is an outspoken supporter of aging naturally and, in what some saw as a swipe at Courteney, said she thinks Botox “looks terrible.”

“Courteney is furious at Jen for taking a backhanded slap at her appearance,” said an insider close to both actresses.

“When Courteney called Jen on her nasty dig, Jen fired back that Courteney should act her age and stop trying so hard to impress her young boyfriend.

“Jen told Courteney that women who don’t allow themselves to age naturally and gracefully are pathetic.”

This isn’t the first time the longtime BFFs have butted heads. Things got tense between them when Jen skipped Cour­teney’s birthday party last year because sources say her control-freak beau, Justin Theroux, wanted her to stop hang­ing out with her old pals.

“They’re both sore right now,” the insider added. “But knowing Jen and Courteney’s tempestuous history, they’ll kiss and make up eventually.”