Strict laws enacted to prevent abuses by users of Airbnb are putting the city’s legitimate bed-and-breakfasts out of business.

That’s because the regulations, meant to keep apartments from turning into illegal hotels — or, in a few notorious cases, brothels — are being applied to B&Bs that have been operating here for years, according to Crain’s New York Business.

Since the 2011 multiple-dwelling law went into effect, regulators have been dishing out hefty fines to building owners who rent out apartments or rooms in residential buildings for less than 30 days.

In that time, the number of bed-and-breakfasts has been cut in half, Mary White, the founder of Bnb Finder, told Crain’s New York Business.

There are now only 15 legitimate bed-and-breakfasts that pay taxes and register with the city.

“I decided to stand up and fight, and it cost me a lot of money,” said Vinessa Milando, owner of Ivy Terrace on East 58th Street.

She told Crain’s that the law, combined with Airbnb, has been like a “one-two punch” for her business, which she has run since 1997.

She is determined to keep operating despite $160,000 in fines and legal fees she has paid over three years.

Some of the violations include not having a sprinkler system in each room and not having separate enclosed staircases for exits in the three-story town house.

Milando founded the nonprofit Stay NYC, whose mission is to carve out an exemption for legitimate B&Bs.

The organization argues that its members have always followed the letter of the law by registering with the city’s Department of Finance and paying the same taxes as hotels.

But many other B&Bs have already shuttered their doors, including the Wyman House on Riverside Drive at West 76th Street.

“It was next to impossible to do business in New York,” said Pamela Wyman, who ran the B&B before selling the house to move to South Carolina.