It was billed as the largest Super Bowl party in South Florida.

The backdrop: poolside of a Miami Beach mansion. An advertisement promises six DJs spinning, a “sensational” bikini contest, flowing liquor and a concert series to cap off the day’s events.

There’s just one problem: It’s illegal, and Miami Beach officials have vowed to shut it down.

“This is super tough,” said Watson James, who helped organize the event.

James does not live in the stately mansion at 6360 N. Bay Rd., but said he knew its owner.

For years, Miami Beach has fought against “party houses” infiltrating residential neighborhoods. The city bans home rentals for less than six months, and prohibits the use of single-family homes for parties to which tickets are sold to the public.

Until recently, the city was getting a handle on the problem, said City Attorney Jose Smith. But with big events in town — like the recent college football national championship — the drinking, dancing masses have returned to Miami Beach’s neighborhoods. City officials have promised anew to crack down on them.

“We’re trying to protect the character of a single-family neighborhood,” said Assistant City Attorney Gary Held.

They also want people to be aware of the issue so they don’t end up paying for tickets to illegal events.

“Party foul,” said city spokeswoman Nannette Rodriguez. “The party does not go on.”

Online ticket prices for Sunday’s planned Super Bowl party ranged from $80 for women to $100 for men and $500 for VIP treatment and your choice of a premium bottle of alcohol, according to a posting on wantickets.com.

James — who said he blogs and was organizing the party under the group name NFL Media Group (which he said is not officially affiliated with the National Football League) — said it started as a get-together with friends to watch the Super Bowl and morphed into something bigger.

“I’ve been looking at other locations to do events like this, but the weather in Miami Beach right now, February — there’s just nothing like it,” he said.

James said he has worked for three weeks to put the party together — bringing in luxury cars from Boca Raton, dancing girls and a 25-foot screen on which to watch the big game.

He said he didn’t know his party was prohibited by the city code until he got a call from a Miami Herald reporter. Then he downplayed the event as “over-hyped.” He said no one had bought tickets as of Wednesday evening.

“I really had no idea, and if the party is cancelled, then cancel the problem,” he said.

Smith, the city attorney, said Miami Beach would send the organizer a letter “asking him not to have the party.”

“When neighbors start complaining, we have to do something,” Smith said.

It was unclear how the city learned of the event.

Rodriguez said the party and the house are “under investigation” by the city’s legal and code departments. City records show that the house has been cited by code compliance, or complaints have been registered at that address, 13 times since 1991.

The home, which according to county property records is owned by Marvin F. Ceder, also was the site of filming of Oxygen’s Bad Girls Club Season 5. Calls to numbers listed in Ceder’s name were not answered.