The two ride-hailing companies had been asked to appear as part of a House Transportation and Infrastructure Committee inquiry on safety, labor and congestion.

"Their failure to appear at this hearing is a telling sign that they would rather suffer a public lashing than answer questions on the record about their operations," the head of the panel, U.S. Representative Peter DeFazio, a Democrat, said at the subcommittee hearing.

DeFazio added the hearing "should also serve also a wake-up call to the companies that have flooded our roadways with disruptive technologies and investor capital that their days of operating with little public policy and regulatory oversight in the transportation space are coming to an end."

Lawmakers raised issues such as safety, congestion, wages and working conditions for drivers. Representative Eleanor Holmes Norton, who chairs the subcommittee, said the hearing was the first serious discussion by Congress to provide "appropriate guardrails to ensure safety and accountability."

Lyft spokeswoman Campbell Matthews said the company has held many discussions with lawmakers and the company "provides economic opportunity for drivers and affordable, reliable transportation for riders. We take this work extremely seriously and believe safety is fundamental to these efforts."

Uber said it shares "Congress’ focus on keeping Americans safe on rideshare. Safety will always be a long-term commitment for us... We have a rich history of productive conversations with this committee and all federal lawmakers - and look forward to continuing to drive towards solutions that keep all users of the platform safe."

Earlier this week, DeFazio urged the companies' to participate in the inquiry even as Uber and Lyft directed lawmakers to third-party industry associations.

DeFazio added "the tenuous existence of Uber and Lyft is literally fueled by millions of independent contractors who see their take home pay reduced drastically – below minimum wage in some states - as they are made to pay fees collected by the company, self-employment taxes and costs associated with operating and maintaining their vehicles."

AFL-CIO official Larry Willis testified that the industry "too often exploits the drivers who provide this service, and intentionally undermines the goals of public transportation."

Two lawmakers at the hearing testified about a bipartisan bill to prod states to require front license plates and codes on both back-passenger side windows that riders could scan on a smart device to confirm their ride. The measure was proposed after a young woman was murdered when she summoned an Uber and got into the wrong car.

DeFazio said the companies, which have reported substantial losses, "don’t make information about their process for deactivating dangerous drivers public. They don’t share data on the prevalence of assaults on their platforms. They don’t reveal details on how drivers are paid. What we do know is that both these companies are struggling since going public... Clearly, this business model is not sustainable."

(Writing by Susan Heavey and David Shepardson; Editing by Bernadette Baum and Chizu Nomiyama)

By David Shepardson