Legalizing app-based sports betting comes with a heavy price: an avalanche of gambling addicts, New Jersey treatment experts are warning New York officials.

The number of people calling New Jersey’s gambling hot line and reporting a sports-betting problem has more than doubled since the Garden State legalized such wagering in June 2018, according to a new report by the Council on Compulsive Gambling of New Jersey which was obtained by The Post.

The Garden State allows people to wager both in person at casinos and off-site through apps, with the overwhelming majority of gamblers, 84 percent, placing their bets online, statistics show.

But New York has only allowed in-person sports betting — currently at four upstate casinos — while wrestling with whether to expand to apps.

Neva Pryor, executive director of the council, advised against it.

“I think it’s better if a person has to physically go somewhere to bet,” she said.

With online apps, it’s like “having a casino in your back pocket,” she added. “It’s always available.’’

The council’s report found that the number of sports-betting calls its helpline received before the 2018 legalization was about 1 to 5 percent of the total, while afterward, that figure doubled to 10.8 percent.

The hotline averages a total of 96 calls a month about any number of addictions, so the sports-gambling ones jumped from as few as one to more than 10, the group said.

Last February, when the Super Bowl was played, that figure soared past 16

Some New York lawmakers and gambling advocates are urging Albany to legalize app-based bets, but the effort stalled earlier this year. Gov. Andrew Cuomo has opposed the move.

But with the state facing an expected $6 billion shortfall next year, political observers have speculated that politicians might be so desperate for revenue that they may reconsider it.

In June, New Jersey surpassed Nevada as the largest state sports bookie, raking in millions of dollars.

The New Jersey council, also headed by Assistant Director Dan Trolaro, spends about $650,000 annually — about a third of its $2 million budget — on radio ads, videos and billboards to publicize its 800-Gambler hotline to let those with gambling disorders know that treatment is available.

But that figure is dwarfed from advertising by gambling interests.

OnlinePokerReport.com estimates that 24 percent of the revenue generated by a gambling operator is spent on advertising.

In New Jersey, that percentage would equate to $79.4 million, according to Pryor and Trolaro.

“Additional funds are desperately needed to heighten awareness of problem and disordered gambling,” they said in a release detailing the council’s report.

The council does not take a position for or against legalized gambling.

But Pryor and Trolaro said they are specifically troubled by “the availability and accessibility of sports wagering.”

Even before sports betting was legalized, a Rutgers University survey found that 6.3 percent of New Jersey residents had a gambling disorder — triple the national average of 2.1 percent.