WWW- Miss USA’s hard-partying lifestyle has landed her tiara-clad head on the chopping block, with pageant boss Donald Trump on the verge of telling the beauty queen: “You’re fired!”

Tara Conner could be dethroned as Miss USA 2006 within a week if Trump decides “behavioral and personal issues” have made the small-town Kentucky girl unworthy of the crown, pageant honchos revealed Thursday.

Those issues include Conner’s alleged substance abuse, failing to make Miss USA promotional appearances, chafing at other obligations and nonstop nightclubbing at Big Apple hot spots, said sources close to her and the situation.

“She makes Paris Hilton look like a baby,” said a source, who confirmed Conner’s conduct has been a concern since summer.

The furor has led Conner to cancel plans to celebrate her upcoming 21st birthday with dual bashes at the Pure club in Vegas, and at Stereo in New York. She did not return a request for comment.

The beauty queen has been romantically linked to two of Stereo’s owners and celebrities who cavort at the NYC hot spot, including MTV veejay Damien Fahey.

Trump, who operates the pageant with NBC, refused to detail Conner’s “issues,” but called the situation “very serious.”

“I’m concerned about her. And I want to make sure that she’s treated really fairly. And I’m also concerned that we do the right thing for the pageant,” said The Donald.

Conner represented Kentucky in April’s Miss USA pageant.