MACAULAY CULKIN flipped out after being snubbed by his ex-lover MILA KUNIS, and now pals fear the troubled actor is headed into another downward spiral!

“Mac made a play for Mila, but she blew him off,” revealed an insider. “After she spurned his advances, he went ber­serk.”

The former “Home Alone” star, 32, reached out to the “Ted” cutie, 29, while they were both in England recently, sources say.

Culkin wanted to rekindle their eight-year romance, even though Mila has been dating Ashton Kutcher, her co-star on the hit sitcom “That ’70s Show,” since April 2012, the sources add.

“Mac was desperate to hook hook up with Mila, and he saw this as his big chance,” explained the insider.

Mila was in England making a movie called “Jupiter Ascend­ing,” and Ashton had yet to join her. “Mac thought it was a great opportunity until Mila deep-sixed the idea,” continued the insider. “Now Mac’s friends fear that he’s so devastated he could wind up in another life-or-death situation.”

Mila’s brush-off boiled over when Culkin left a nightclub in Brighton, a seaside town in southeast England, in the early hours of April 16.

Reports say he lunged at a photographer as he walked over to a van, screaming at the shutterbug and telling him to “go to hell.”

Culkin was also bizarrely dressed in Ray-Ban Wayfarer sunglasses and a scarf that cov­ered up the lower part of his face, similar to a getup favored by his late pal Michael Jackson.

The “Richie Rich” star was in England to join the tour of his buddy Adam Green and his band “The Moldy Peaches.” But he hardly looked like a star. During a stop in east London, one fellow clubgoer actually thought Culkin was homeless.

“We chatted for about five minutes and he said he was here visiting friends,” recalled student Marley Spindler, who met Culkin outside the Village Underground, a multipurpose events warehouse for concerts and nightclubs.

“He was vacant, speaking very quietly and mellow. He looked spaced out. I didn’t recognize him at first. I thought he was some homeless guy scrounging a smoke.”

A second source added: “His weird behavior and looking like a gutter rat in London doesn’t bode well for Mac getting back on the straight and narrow.”