The de Blasio administration plans to ram through another $43 million in ferry purchases for its money-pit fleet — in the face of objections from the city’s fiscal watchdog, The Post has learned.

The push comes just months after City Hall forged full speed ahead with another $84.5 million purchase over the worries of City Comptroller Scott Stringer.

It swells the total amount sunk into the program to $637 million.

The decision “to deem another City tax-payer funded vessel purchase registered without providing exhaustive data, metrics, reports, etc. to demonstrate the success of the citywide ferry program and justify the ballooning costs of this initiative is disappointing,” Stringer wrote in a letter Friday to the Economic Development Corp., a copy of which was obtained by The Post.

The $43 million covers the purchase of five new boats, according to purchase documents submitted to the Comptroller’s Office.

It marks the second time this year that City Hall has exercised veto power to torpedo Stringer’s attempts at oversight of the ferry system.

The East River system is among Mayor de Blasio’s biggest transit initiatives, despite carrying only a fraction of the New Yorkers who use the subways, buses or CitiBike.

Just 18,000 people rode the ferries on an average weekday during the spring, with those trips subsidized at a rate of $10.73 per ticket.

Meanwhile, 5.4 million people ride the rails, and 1.8 million hop a bus each weekday on average. And more than 62,000 CitiBike trips were made daily in May.

The EDC nevertheless accused Stringer of trying to scuttle New Yorkers’ search for a nautical commuting option.

“NYC Ferry is growing, and making sure we have an adequate fleet is just smart planning,” said spokeswoman Stephanie Baez. “The comptroller should stop trying to stand in the way of New Yorkers who just want a better commute.”

Although the state controls the MTA, transit advocates have assailed City Hall’s repeated insistence on pumping money into the ferry system rather than funding bus and bike infrastructure.

“While the city shells out millions more for lightly used ferries, New Yorkers continue to abandon slow, unreliable bus service,” said Ben Fried, of the straphanger-advocacy group Transit Center. “There should be a moratorium on ferry expansion until the mayor meets his goal of speeding up buses 25 percent.”

Bus riders agreed.

“Every single day I ride the bus, and every day I’m late for something,” said Ramon Mendez, 36, a clothing-store manager.

“I’m late for work, I’m late for dinner, I’m late to pick up my daughter . . . Ferries are for tourists. Build me a better bus.”

Additional reporting by Joseph Konig and Aaron Feis