The recall of about 1.7 million General Motors Co. vehicles for ignition switch defects linked to 13 deaths has renewed congressional scrutiny of the federal agency charged with regulating highway safety.

House and Senate committees looking into GM’s handling of consumer complaints about the defects are also investigating the National Highway Traffic Safety Administration’s response. Critics say regulators were slow to identify a pattern of similar complaints and lagged in responding.

The GM case evokes memories of the 2009 recall of more than 10 million Toyota vehicles worldwide, when lawmakers also questioned whether NHTSA reacted quickly enough. In response, Congress increased to $35 million the maximum penalty that NHTSA can assess for violations of reporting and recall regulations.

Despite that enhanced authority and the lessons of the Toyota case, highway safety advocates say NHTSA’s response to GM’s problems was inadequate. Some safety advocates are urging lawmakers to subject NHTSA to the same scrutiny as the automaker.

“Just as GM President Mary Barra has commissioned an independent investigation of why GM did not do the recall and remedy … at least nine years earlier, there needs to be a similar independent investigation of NHTSA’s failure to act,” Clarence Ditlow, executive director of the Center for Auto Safety, said in a letter to NHTSA’s Acting Administrator David J. Friedman. “People died and the agency shares responsibility for their deaths with GM.”

At issue is GM’s handling of complaints about faulty ignition switches in some Chevrolet, Pontiac and Saturn models that could switch off while a vehicle moved at high speeds. The carmaker began looking into problems with the switches as long ago as 2004.

Connecticut Democrat Richard Blumenthal, chairman of the Senate Commerce, Science and Transportation subcommittee with jurisdiction over safety issues, wrote to Friedman earlier this month requesting documents that he said would be “crucial in understanding why NHTSA failed to initiate a full investigation of the defects and issue a recall earlier.”

Blumenthal has challenged NHTSA’s contention that there was no critical mass of complaints to identify a pattern. Blumenthal said many of the accidents stemming from the ignition switches “were well-documented and logged in NHTSA’s complaint database” but never acted on.

A law enacted in 2000 (PL 106-414) in reaction to a pattern of SUV rollovers requires automakers to promptly report to NHTSA any information that suggests a potential safety defect.

“If numerous media reports are correct, NHTSA’s inaction allowed hundreds of thousands of unsafe vehicles to continue operating on America’s motorways and exposed millions of drivers to unnecessary danger which ultimately resulted in horrific and untimely deaths,” said Sen. Patrick J. Toomey, R-Pa.

House Energy and Commerce Chairman Fred Upton, R-Mich., has expressed frustration that the GM problems nevertheless went unnoticed. He said NHTSA chief Friedman’s testimony would be “essential to getting answers about what went wrong.”

New GM Chief Executive Mary T. Barra is also expected to testify to Upton’s panel next week.

Safety advocates including Ditlow and Public Citizen President Emeritus Joan Claybrook, who led NHTSA during the Carter administrator, said a big problem facing regulators is inadequate resources. Congress, they suggest, has itself to blame for not appropriating enough money to get the job done.

At hearings that followed the Toyota recall, Claybrook told lawmakers that NHTSA’s annual vehicle safety budget should have been “doubled” from its level of about $133 million. But in fiscal 2014, the agency’s appropriations for such programs increased to just $134 million.