Relatives of a family killed in a high-speed crash that highlighted safety flaws of Toyotas and led to the recalls of millions of vehicles have sued the world's largest car maker, according to a lawsuit filed today.

The lawsuit filed in San Diego County Superior Court names Toyota Motor Corp, Toyota Motor Sales USA, other Toyota US entities and El Cajon Luxury Cars. It seeks unspecified damages for product liability and negligence.

California Highway Patrol officer Mark Saylor, 45, his wife Cleofe, 45, their daughter Mahala, 13, and Cleofe's brother Chris Lastrella, 39, were travelling on a freeway near Santee, California, on August 28 when their Lexus car reached speeds of more than 120mph, hit another utility vehicle, careered off an embankment, rolled several times and burst into flames.

Investigators found that a wrong-sized floor mat that trapped the accelerator was the cause of the crash.

A haunting emergency call captured Lastrella telling the others to pray before the car launched off the embankment.

According to the lawsuit, the Lexus ES350 "began to accelerate on its own". Saylor attempted to apply the brakes and do everything possible to stop the car, but he was unable to do so, the lawsuit said.

After the crash, Toyota recalled millions of cars to replace floor mats that it said could cause the accelerator to jam. The motor giant later recalled millions more vehicles to replace accelerator pedals it said could stick.

Last week, company president Akio Toyoda apologised to Congress, millions of Toyota owners and to the Saylor family specifically during a hearing before the House Oversight and Government Reform Committee in Washington DC.

Fe Lastrella, the mother of Chris Lastrella and one of the plaintiffs in the lawsuit, testified at that hearing.

"I'm here to speak for my four children and for the safety of the consumers through the world," she told the committee. "You don't want another family to suffer like we are suffering."