US banks are imposing stomach-churning and often hidden fees — some with gargantuan, five-digit interest rates — that force as many as 25 million poorer millennials and Gen Xers to go unbanked, according to the latest studies.

“Millennials are a large portion of the group now being pushed out of the system, along with other lower-income people who are economically distressed,” Alex Tabb, chief operating officer of Tabb Group, a financial markets research firm, told The Post. “It just so happens that more millennials are in the lower-income group today.”

And in a report for the podcast “Wall & Broadcast,” Tabb and co-host Dan Simon discover that millennials — a cohort of some 75 million Americans 18 to 34 — are not voluntarily quitting banks in droves just for the lure of high-tech alternatives, as is popularly assumed.

It’s more because of the mafia-style fees banks are charging.

The “Wall & Broadcast” report, which talked to millennials, some unbanked, did not single out any individual banks, but in reviewing the entire sector, the podcast noted:

The majority of debit card overdraft fees are on transactions of $24 or less.

The majority of overdrafts are repaid within three days.

In lending terms, a consumer borrowing $24 for three days and paying the median overdraft fee of $34, effectively carries a 17,000 percent annual percentage rate.

An unbanked consumer pays as much as 2 percent of the face value to cash a check at a facility such as Western Union in New York.\

Another curse is the multiple compounding of overdraft fees. For example, a customer can unwittingly incur a $34 overdraft protection fee if he or she uses a debit card to pay $12 for a movie ticket with only $10 in his or her account. If the customer then decides to purchase a $4 ice cream after the movie with the same card, he or she will be hit up for another $34 — for total fees of $68.

“This purchase protection is basically a short-term loan with very expensive pricing,” Tabb said.

And some banks no longer want the millennials’ business when they fall behind on fee payments.

Though banks are losing ground to tech startups, it’s the massive fees that drive many poor millennials out, the studies show.

About 37 million US adults do not have bank accounts today — and two-thirds, or roughly 25 million, are millennials or Gen Xers, and three times more likely to be unemployed than bank consumers.

A full 10 million US households now have either zero or few bank services, or were unceremoniously dumped by banks who regarded them as high risk. Since 2008, payday and alternative lenders have been having a field day, as nearly $150 billion dollars of bank credit has been removed from the weakest consumers.

“The banking system in general has not evolved enough with fees that encourage lower-income millennials to stay,” said Christine Barry, an Aite Group analyst who recently conducted a separate banking study of millennials.

In 2013, Americans spent $32 billion on overdraft fees, or three times as much as they spent on breast and lung cancer treatments combined, according to BankMobile, an online bank that gathered the data for research on what makes millennial and other customers tick. It so happens that many bank customers have had it with high fees.

“It is damn expensive to be poor in this country,” Amit Sharma, co-founder of Empowerment Capital, told the “Wall & Broadcast” podcast, referring to how bank fees disproportionally crimp poorer consumers.

“And it’s not transparent to the customer.”

The government’s Consumer Financial Protection Bureau has raised alarm bells about the controversial impact of “opting-in” to such overdraft services for debit and ATM cards.