WASHINGTON – Sen. Schumer listed job openings for unpaid interns — but said the posting was “made in error” after Rep.-elect Alexandria Ocasio-Cortez criticized members of Congress for seeking free labor.

Ocasio-Cortez is promising to pay $15 per hour to her interns.

Shortly after advertising for unpaid press and legislative interns, Schumer’s office said that was a mistake.

“This posting was made in error. Starting in January, Senator Schumer’s office will offer a stipend to eligible interns,” Angelo Roefaro, spokesman for Schumer, told The Post.

Schumer’s office is still determining how much the stipend will be worth and which interns would be eligible for pay.

Previously, Schumer and fellow New York Democrat Kirsten Gillibrand didn’t pay their interns, according to data collected in 2017 by the advocacy group Pay Our Interns.

Without a paycheck to cover housing in high-cost DC, advocates warned that the pipeline to power was increasingly being closed off to low-income students and people of color.

Ocasio-Cortez came to Washington promising to pay her interns at least $15 an hour – a rarity.

There are just three other members of Congress tracked by Pay Our Interns that offer that rate: Vermont Sen. Bernie Sanders, Alabama Sen. Doug Jones and Washington Rep. Adam Smith, who introduced legislation in September to mandate a $15 wage for all full-time interns.

Ocasio-Cortez, a Democratic socialist, said it’s “unjust” for politicians to get paid a living wage, but rely on unpaid interns and low-wage aides.

“Gotta love the rich irony of Congressmen asking ‘how are you going to pay for it?’ suddenly grow awfully quiet when called out on their expectation that part-time workers magically invent money to work for free,” she tweeted Monday, without mentioning Schumer.

Schumer got his start on Capitol Hill as an intern in 1969 to New York Rep. Bert Podell and earned about $1,800 a month in today’s dollars, according to Washington Monthly.

From 1974 to 1994 there was a regular funding stream to pay interns through a program called the Lyndon Baines Johnson internship program.

When that funding dried up, it was up to each member’s office to decide whether to continue paying interns.

Many decided not to pay because that would eat into the salaries of their full-time staff, which averages about $51,000 – well below the median household income of $76,000 in DC.

Pay Our Interns found that only 8 percent of GOP house members offered money to interns, and 4 percent of Democratic members, in 2017. The situation was a bit better in the Senate with 51 percent of Republicans and 31 percent of Democrats funding internships, the report found.

After getting shamed for the unpaid labor, Congress took action this year and approved $8.8 million in the House and $5 million in the Senate for internships.

That amounted to about $20,000 for each House member. In the Senate, Schumer and Gillibrand got $65,400 each for intern salaries, according to a legislative summary viewed by The Post.

“After having pushed for this cause for the past two years, it feels good to see the pendulum swing in our direction,” Carlos Mark Vera, founder of Pay Our Interns, told The Post.

He cautioned the work is not yet over until all interns are paid and the positions don’t “simply go to the children of donors but to actual working-class youth.”