Backstreet Boy Nick Carter started the New Year off on the wrong foot when he was arrested after getting drunk, getting into a fight — and then exposing himself!

Now his worried friends are trying to get him into an alcohol rehab program.

Before the melee, the 21-year-old heartthrob got soused and rowdy in a Tampa, Fla., club on New Year’s Day, according to witnesses.

When a young woman tried to calm him down, he became belligerent — and then argued with cops, who hauled him off to the slammer.

“Nick just kept hollering,” said a witness. “The young woman was telling him he was ‘out of order,’ but he wasn’t listening. He just shouted louder and louder.

“The police — who were at the club for another disturbance — told him to knock it off. And he wouldn’t listen to them either.”

Tampa police spokesman Joe Durkin said officers asked Carter to quiet down and leave the Pop City club at least 10 times. “It was 3:20 a.m. They finally told him to leave by the count of three or be arrested. He was arrested.”

Carter was handcuffed and hauled off in the backseat of a cruiser to the station-house, where the Backstreet Boy was charged with a misdemeanor offense of resisting or opposing a law enforcement officer without violence.

He was released on his own recognizance and is to appear in a Tampa court on March 4.

The blond, 6-foot singer and drummer told friends afterward, “I wasn’t resisting. I just didn’t move fast enough.”

Witnesses said Carter arrived at the club on New Year’s Day evening with several friends and began drinking heavily. When a drunken pal puked in the men’s room and security guards tried to eject him, Carter scuffled with them, a club employee told The ENQUIRER.

Nick Carter’s nickname is “Chaos.”

“He was allowed to remain in the club, but he just got rowdier as the night wore on,” said the employee.

At one point during the evening, other clubgoers called local radio station WFLZ to report that the youngest member of the popular five-man group was exposing himself and shouting, “Hey, everybody! I’m Nick Carter.”

Carter is not the first of the Backstreet Boys to get in trouble with alcohol. Band member A.J. McLean went into rehab last July as a result of alcohol abuse and his absence forced the band to postpone its U.S. and Canadian concert tour. Now friends worry that Carter is headed for trouble, too, and feel he should do as A.J. did and go into an alcohol rehab program.

“I know A.J. is trying to convince Nick to follow his example and go into rehab to clean up his act,” said a mutual friend. “But Nick won’t listen.

“It’s too bad, because A.J. is doing well and has been for a while now.”