Fare-beating is now costing the MTA more than 6 percent of its subway and bus revenue. The agency needs to stop the bleeding — but it deserves more help.

Last month, MTA Inspector General Carolyn Pokorny warned that the agency wasn’t measuring turnstile-jumping properly, and the board is now admitting the problem.

An experiment in posting MTA cops in three major subway stations told the tale: Virtually no fare evasion in sight of the police, but lots of jumpers at entrances without visible enforcement.

The report to the board Monday blames a citywide culture that’s grown tolerant of this abuse, an attitude “that’s sort of developed over the last few years that we are going to have to try to change,” said Patrick Warren, the MTA’s chief safety officer.

Manhattan DA Cyrus Vance and Brooklyn DA Eric Gonzalez are part of the problem: They’ve decided not to prosecute over a minor theft. But all those $2.75 robberies add up to an estimated $300 million this year, double the level of 2017, and a good chunk of the MTA’s $4.5 billion in fare revenue. NYPD brass have also ordered more lenient enforcement.

To make things worse, two Assembly Democrats from Manhattan, Dan Quart and Yuhline Niou, want to cut the fine from $100 to $2.75 — an open invitation to jump the turnstile.

The MTA is hiring 500 new transit cops, who may make a difference. But it deserves support — instead of being undermined by other government agencies.

There’s no excuse for fare-beating. Low-income commuters can get half-price MetroCards via the city’s Fair Fares program.