And you thought the Park Slope mommies had a monopoly on being busybodies in Brooklyn.

After nosy Ditmas Park resident Joel Siegel noticed a slew of cars with Iowa license plates clogging his Brooklyn neighborhood, he didn’t just shrug it off — he sparked a bi-state probe.

Siegel, a lawyer and president of the Ditmas Park West Neighborhood Association, sent authorities in the Hawkeye State and New York a list of 20 cars registered in Iowa but parked in Brooklyn.

“A lot of people are unhappy because it’s hard to park now with the proliferation of these Iowa plates,” he said. “Our neighborhood is very small. It’s a pain in the ass.”

Siegel’s letter linked the vehicles to a rental-car business on Coney Island Avenue that operates under a variety of names, including 25 Dollar Car Rental.

The Des Moines Register said Iowa officials suspect the plates may be a scheme to avoid New York insurance rates. The median cost of auto insurance here is $1,062 a year; in Iowa, it’s $530.

A call to 25 Dollar Car Rental wasn’t returned.