(Bloomberg News) The "unnatural relationship" between President Barack Obama's administration and automakers that received U.S. bailouts may explain the delay in disclosing a potential safety defect in General Motors Co. Chevrolet Volts, Republican lawmakers said in a report.

The House Oversight and Government Reform Committee report, released before a hearing today at which GM Chief Executive Officer Dan Akerson testified, questions whether the government's 32 percent ownership of the automaker led it to delay publicizing a June 6 fire in a Volt lithium-ion battery that happened three weeks after a crash test.

"This unnatural relationship has blurred the lines between the public and private sector as President Obama touts the survival of General Motors as one of the top accomplishments of his administration," according to the report by the committee headed by Representative Darrell Issa, a California Republican. "On a policy level, this relationship raises serious questions about whether or not the administration is too heavily invested in the success of GM to be an effective regulator."

Today's hearing stems from the Volt fire and followup testing by GM, based in Detroit, and the U.S. National Highway Traffic Safety Administration that found battery coolant can leak and catch fire in a simulated rollover crash that punctures the battery compartment.

Delay Defended

NHTSA Administrator David Strickland and Akerson defended the five-month delay in notifying the public about a possible Volt defect after the fire at a NHTSA test facility, saying it took time to determine the cause and what risk it might pose to Volt drivers.

"Not only would I drive it, I would drive my wife, my mother and my baby sister," Strickland said today when asked by Representative Dennis Kucinich, an Ohio Democrat, whether the Volt is safe.

GM and NHTSA didn't disclose the fire until Bloomberg News reported it in November. The agency opened a formal investigation later that month and closed it last week, saying electric cars posed no more of a fire risk than gasoline-powered models, after GM announced a fix for current and future Volts, avoiding a formal recall.

GM defended the Volt today in a full-page ad in media including the New York Times and the Wall Street Journal with an open letter from Akerson calling the car a "technological moon shot" and safe.

"Yes, the world is learning from Detroit again," he wrote. "And we couldn't be prouder."

'Disproportionate' Scrutiny

Akerson, who said he just bought a Volt, and Strickland appeared before a congressional panel overseen by Issa, who has criticized the Obama administration's electric-vehicle goals and the U.S. bailouts of GM and Chrysler Group LLC.