Mayor Bill de Blasio and the City Council would destroy popular ride-hailing app Uber's New York operation with their proposal to temporarily cap the number of new vehicle licenses, an Uber executive said Wednesday.

"It's going to hurt the system," Josh Mohrer, the company's New York City general manager, told Crain's. "It's going to break it."

Mr. Mohrer ticked off a list of possible repercussions if the council passes a bill proposed by the Taxi and Limousine Commission to limit new for-hire vehicle licenses issued by the city: Uber cars would take longer to respond to passengers, fares would increase, customers would flee the service and surge pricing would become more common.

He claimed the proposal was suspiciously similar to one made earlier this year by the Committee for Taxi Safety, an industry group. City officials said their proposal was not influenced by that group. A spokeswoman for the organization did not respond to a request for comment.

"It basically would make Uber unreliable," Mr. Mohrer said. "Clearly this is the taxi industry trying to stop us."

The proposal was announced a day after Uber celebrated a victory over the traditional taxi industry, having persuaded the TLC to pass rules without several proposed provisions that the company opposed. This new bill, introduced by Councilmen Ydanis Rodriguez and Stephen Levin, would limit Uber to 1% growth for at least a year while the city studies the effect of the for-hire vehicle industry on traffic congestion, pollution and quality of life.

The announcement caught Uber and its e-hail rivals, such as Lyft, off guard. City officials had kept is close to the vest. Only just before the proposal was unveiled did First Deputy Mayor Anthony Shorris and TLC Commissioner Meera Joshi make calls to business groups and transportation advocates seeking support for it, sources said. Ms. Joshi and Transportation Commissioner Polly Trottenberg were said to have canceled other plans at the last minute to participate in a hastily-arranged conference call with reporters Tuesday afternoon. Spokespeople for Ms. Joshi and Ms. Trottenberg denied any rescheduling took place.

A 1% cap would limit Uber's growth to 201 drivers for a year. In March, the company told Crain's it planned to add 10,000 drivers by the end of 2015. Uber's app is currently is used by 26,000 drivers in New York City, according to the company.

Asked if the bill would harm Uber's city revenues, which has been conservatively estimated to be $130 million a year, Mr. Mohrer said it would. "That's secondary to me right now, in terms of trips, in terms of economic opportunities for our driver-partners, in terms of reliability for consumers," he said. "It would be bad for the company economically, but it would also be bad for the city."

Mr. Mohrer claims that Uber's service, especially its car-pool option, takes cars off the road, not the opposite. But a TLC spokesman cited U.S. Census figures showing car ownership in New York City remained flat between 2009 and 2014, with 45.6% of households owning vehicles. That statistic doesn't reflect the use of those vehicles, however. Uber has been growing steadily in the city since 2011.

On Tuesday, the city forwarded a slideshow to reporters that suggested that explosive growth in the number of for-hire vehicles has led to a 9% decline in average speeds in Manhattan between 2010 and 2014. Mr. Mohrer said that data seemed "oddly selected," noting it used as its baseline 2010, a "uniquely fast year" by city standards with an average speed of 9.3 miles-per-hour, and compared it with 2014, when Mr. de Blasio's speed-reducing Vision Zero plan was launched.

A spokesman for the mayor strongly disagreed with Mr. Mohrer's argument, saying, "There is no comparison between Vision Zero's focus on eliminating excessive and fatal speeds and data showing already congested traffic in midtown slowing even further to a crawl."

The city already limits the number of yellow and green taxis in operation, and grants those vehicles the exclusive right to pick up street hails. Uber vehicles respond to hails made via smartphone. Recent lawsuits by taxi-medallion owners and lenders against the city argue that e-hails are the same as street hails and thus Uber vehicles should not be allowed to respond to them.