WTF! DIDDY'S TOO COOL FOR HIS OWN PARTY!

Have Sean (Diddy) Combs’ parties become so low-key that even he doesn’t want to attend?
Insiders say the hip-hop artist, who once made headlines with his lavish social events, threw a spur-of-the-minute shindig at his East Hampton digs on Labor Day, but didn’t show up to play host until hours after its noon start time.

Not that he missed anything.

Diddy’s spokeswoman tells us that unlike his lush “White Parties” of summers past, Monday’s soiree was “no party,” but rather “a small gathering.” Nonetheless, our insiders were still surprised by its lack of celebrity star power.

One source says Diddy’s decision to host the Labor Day gathering was a spur-of-the-moment plan hatched at the raucous birthday party last Saturday that hip-hop magnate Jay-Z threw for his wife, Beyoncé, at Richie Akiva and Scott Sartiano?a>??s new but yet-to-open Chelsea supper club, the Darby.

In attendance there were Serena Williams, Alicia Keys, Kanye West and Diddy, who after staying out all night in Beyoncé’s honor, one source says, left straightaway for the Hamptons to organize his affair. That plan included hiring DJ Cassidy, who oversaw tunes at the Beyoncé bash, to spin for Diddy’s East End guests.

Though he planned the party to run from noon to 7 p.m., our sources say Diddy didn’t actually roll into his own party until 5 p.m. (One partygoer says he did make a brief appearance around 2, however.)

By the time he arrived, we hear the crowd had dwindled from about 100 to 60 and was light on the recognizable names and faces that graced the Beyoncé event.

One celebrity who did attend was singer Cassie. An insider says Diddy’s rumored girlfriend of years was the “unofficial hostess” of the party and “didn’t leave Diddy’s side the whole time.”

That source speculates Diddy kept his Labor Day event last-minute and under the radar because his last official Hamptons White Party, on Sept. 2, 2007, caused a ruckus with some of the rapper’s neighbors, who summoned the police.

The 2007 party boasted a mandatory all-white dress code, to match its all-white decor. This year, however, we hear Diddy stuck with the white decor but slacked off on the outfit. He wore a red shirt and white pants, and guests wore a variety of colors.

At least they didn’t look boring.