Some Big Apple politicians are “concerned” that back-door entry on MTA buses won’t ever come to fruition — despite the agency having the right hardware already installed which would help speed up bus times.

The pols, led by Manhattan Borough President Mark Levine, voiced their frustrations in a May 13 letter to MTA CEO Janno Lieber.

“The MTA has already done the hardest part, which is to install OMNY readers at every door,” Levine told The Post on Thursday. “I am perplexed by why they would go through all the expense and effort to install OMNY readers at every door and not turn them on.”

Levine was referring to the completed installation of “OMNY” tap-and-go readers early last year, but the MTA has yet to turn them on — in part, they say, because nine in 10 bus riders still pay with cash or MetroCards.

But Levine said the technology is key to implement “all-door boarding” which he says is “the fastest and quickest way to speed up buses” by reducing the amount of time spend loading and off-loading passengers.

MTA officials earlier this month told local bus drivers to set their consoles so that the back doors only open upon request, citing concerns about fare evasion through the back door.

Nearly one-third of bus riders do not pay their fare, according to the MTA’s most recent surveys. That number has increased since the COVID-19 pandemic, when the MTA briefly made buses free by requiring all riders to enter through the back door.

Levine, whose letter was also signed by seven city council members, acknowledged the MTA’s fare evasion challenges — but said transit leaders need to figure it out.

All-door boarding already exists on the MTA’s “Select Bus Service” lines, where cash and MetroCard users pay off-board. Buses on the M79 spend 21% less time at stops now than they did before the line converted to Select Bus Service, the letter noted.

“Systems around the world do it this way, and they also have to deal with fare evasion,” Levine said, citing fare inspectors in London as an example.

“They do what the MTA is already doing on its SBS buses. Knowing you might be checked, for most people, will be an incentive to pay their fare.”

The MTA did not comment on the substance of the letter.

“We appreciate that the Council Members and Borough President understand our concern with fare evasion on a system where currently one out of three bus riders evades the fare,” MTA rep Mike Cortez said in a statement. “We look forward to working with them on impactful measures that will increase bus speeds including new bus lanes, camera enforcement and route redesign.”