A Brooklyn lawmaker on Tuesday ripped Mayor de Blasio’s $2.7 billion plan for a streetcar service connecting the Brooklyn and Queens waterfronts, saying it’s a “terrible” idea and “an example where the emperor has no clothes.”

City Councilman Carlos Menchaca later doubled down on his remarks by tweeting video of a cartoon where an emperor is marching in his underwear before a shocked crowd.

The tweet says, “Just letting the emperor know he has no clothes. #NoBQX”

During a hearing at City Hall, Menchaca ripped the mayor and his proposed 16-mile streetcar line from Red Hook to Astoria during testimony by transit chief Andy Byford about his 10-year-plan to fix the subways.

“Your visionary plan is in conflict, I think, with this idea that no one likes except for developers and can have an impact … on your plan if so much energy is going from the [government ] agencies into this plan,” Menchaca told Byford.

Menchaca, who represents Red Hook, said “one singular person … likes” the Brooklyn-Queens Connector, or “BQX” project, and he “happens to the mayor of the City of New York.”

Byford tried to avoid the controversy by saying, “I am not going to get into the politics. I am aware of the BQX.”

He pointed out that his agency’s goal is to make the “existing transportation system work better.”