The de Blasio administration is pressing ahead on its long-stalled planned plan to halt horse-drawn carriages from operating in the city, hiring a consultant to review how a ban would affect the city, but some are questioning whether that consultant can be impartial, considering the firm's links to the anti-carriage movement.

Horse carriages still trot in Central Park, but what would the city be like if they are outlawed? That's the question City Hall hired a consultant to figure out.

Its conclusions will play a key role in what promises to be a contentious floor fight in the City Council. It has the final word on the ban.

But even before the report is done, horse carriage drivers are already calling foul.

"It just smells bad, that's all," said Demos Demopoulos of Teamsters Local 553.

The consultant is supposed to be impartial, and the city says it is. But drivers counter that the hired firm can't be trusted. Here's why: the president and CEO on the firm's website has lent support to NYCLASS, the leading group pushing the ban.

"Isn't it obvious that if he's a supporter of banning the industry, it's not an unbiased opinion? It's lopsided," Demopoulos said.

The CEO's name is also on a flyer, along with numerous others.

Langan declined comment.

The firm also lists as a client the company long led by NYCLASS' founder. It's also working to develop the Far West Side. Horse carriage drivers say their stables are valuable real estate.

"We believe it's tainted," Demopoulos said.

NYCLASS says that complaint shows the other sides quote desperation, and a de Blasio spokesman says the firm is chosen for its long track record, adding, "We have complete confidence in their abilities. Disqualifying an applicant based on the personal beliefs of an individual is not only outside the scope of contract evaluations, but would be a clear violation of procurement law and the First Amendment."

Polls show drivers winning public opinion, but environmental law scholar Michael Gerrard says legal cases focusing on impartiality are rarely successful. Plus, a legal challenge would have to wait until the report's done.

"You can't have incremental lawsuits along the way, challenging each step of the process," Gerrard said. "You have to wait until the end, and only then is it ripe for litigation."

The study isn't expected to be completed until at least this summer.

Under the bill, horses would be banned beginning June 2016.