(Bloomberg) -- Uber and Lyft suffered a setback in their months-long fight against rules that could force them to reclassify California drivers as employees.

The ride-hailing companies, along with other businesses that depend on gig-economy work, have been talking with unions about potential deals that could exempt them from state rules making it harder to treat gig workers as independent contractors and avoid additional employment costs.

One of those unions, the International Brotherhood of Teamsters, told California’s governor Thursday it’s against proposals to grant technology platform companies a pass. The move was conveyed in a letter sent by California’s State Building and Construction Trades Council on behalf of a list of affiliates including the Teamsters. It’s a blow to companies’ efforts to avoid making sweeping changes to their businesses.
A top California Teamsters leader called out the ride-hailing companies more directly in a Thursday interview. Randy Cammack, president of the Teamsters council covering southern California, said that he is in “full agreement” with the building trades letter and opposes any exemptions for Uber or Lyft from the state’s new standard for who’s an employee. “You give these guys a break, and all these other employers would say, ‘Well, why shouldn’t we be exempt?’” he said. Cammack said his council participated in talks with Uber, but “won’t be attending any more” in the future. “Everything that I’ve heard that they want to do, I’m in total opposition to,” he said. Uber’s growth has already hurt Teamster industries like delivery, said Cammack.