Toyota, which admits knowing about accelerator problems on some of its vehicles about three years ago, is facing a torrent of criticism that it responded improperly to even earlier alarms.
The largest US auto insurer, State Farm, said on Tuesday it had alerted federal safety regulators on numerous occasions starting in 2007 about an increase in reports of unexpected acceleration in Toyotas.
Toyota US president Jim Lentz has acknowledged that the company new about an accelerator pedal problem on a Tundra bakkie in 2007.
"But we could never really pinpoint the cause of that sticky pedal," he said.
Lentz strongly denied accusations that Toyota had downplayed recurring problems, saying the first reports of unintended acceleration on Toyota models in the US were received late in 2009.
The US National Highway Traffic Safety Administration opened a preliminary investigation in March 2007 of complaints of sticky accelerator pedals on Toyota's luxury-brand Lexus ES350, identifying floor mats as a possible cause.
That probe was closed at the end of 2007 after Toyota issued its first recall over the floor-mat problem.
This week Toyota announced the recall of 437 000 hybrid vehicles, including the Prius, because of a separate braking problem. Japanese transportation chief Seiji Maehara publicly rebuked Toyota president Akio Toyoda, saying the company should have been quicker to recall vehicles with a brake flaw.
Maehara said: "I wish you had taken measures earlier rather than simply saying it was not a major technical problem."
US lawmakers, meanwhile, are investigating whether Toyota and the government had reacted properly to years of complaints. Reform committee member Darrell Issa said there were "unresolved complaints documenting incidents of unintended acceleration in Toyota vehicles as early as 2003".
"Evidence suggests that for nearly a decade, both Toyota and officials at the National Highway Transportation Security Administration were aware of complaints related to unintended acceleration," he said, adding: "I have serious concerns about the agency's actions under the previous administration." - AFP