​ROCKAWAY BEACH — The city has pulled the brakes on a Citi Bike competitor's plan to launch a bike sharing pilot at the beach.

A lawyer with the Department of Transportation sent a cease-and-desist letter on Friday to Skinny Labs Inc., which owns bike sharing service Spin, after the company announced its plan to offer a demo of its program at a press conference with Councilman Eric Ulrich in Rockaway Beach on Monday.

"Please be advised that you do not have the authorization or permission, pursuant to a concession, franchise, permit, contract or otherwise, required for such operations," Michelle Craven, senior executive director of Cityscape & Franchises at the DOT, wrote to Derrick Ko, Spin's co-founder and CEO.

Craven ordered that Ko immediately stop any bike share operations in the five boroughs, saying the city will "actively enforce all laws and its police powers, including but not limited to those that protect its rights of way and ensure the safety and service provided by the city’s rights of way."

Spin, which operates in Seattle and Dallas, offers GPS-activated, self-locking bikes that skip the familiar Citi Bike dock and allows riders to park them with a kickstand, according to officials. Bikes are located and unlocked using an app.

A spokesman with DOT said that while they're interested in new bike sharing technology, it "can't be the Wild West" with random companies setting up shop in the city.

"The public has an interest in a fully-integrated and expanding public bike sharing program that embraces the latest technology," spokesman Scott Gastel said. "We are currently exploring the next phase of expansion, and are considering this new technology’s potential to enhance those plans."

Spin decided to postpone its demo planned for Monday, but will still hold a press conference to discuss the program.

"We are glad the city recognizes the potential that dockless bikeshare can have on underserved communities like the Rockaways," company spokesman George Lence said in a statement.

"We welcome our planned, robust conversations with NYCDOT to help bring our innovative model of transportation to New York City. It reaffirms our commitment to working closely and collaboratively with governments to provide innovative transportation options to cities that are affordable, equitable and eco-friendly."

Ulrich, an outspoken critic of the mayor, accused Bill de Blasio of siding "with the special interests over the people of New York City" by demanding that Spin halt operations.

"The Mayor would rather protect a public monopoly like CitiBike — which barely exists outside of Manhattan — than expand sensible bike sharing in neighborhoods that need it most," he wrote in a statement. "New Yorkers are starving for transportation alternatives and Mayor de Blasio shamefully says, 'let them eat cake.'"

So far, the only Queens neighborhood to get Citi Bike is Long Island City, though it's expected to expand into Astoria in the coming months. It's unclear if or when the service would come to Rockaway.

Spin had planned to bring up to 150 of their bikes to the peninsula in partnership with Paul's Bicycle Shop on Beach 116th Street in Rockaway Park.

Christian Torres, the head mechanic at the shop, said they'd planned to assemble the Spin bikes this weekend ahead of Monday's event, and didn't think Citi Bike would affect the peninsula.

"We don't have Citi Bikes in Rockaway," he said.