WASHINGTON (Reuters) - Toyota Motor Corp apologized for letting safety standards slip during a period of fast growth and vowed to respond more quickly to consumer complaints as two days of congressional hearings crucial to the automaker’s reputation began on Tuesday.

President Akio Toyoda said he was “deeply sorry” for accidents caused by safety problems with Toyota vehicles and detailed a set of reforms that would shift control of recall decisions away from the automaker’s Japanese headquarters.

The world’s largest automaker is seeking to repair damage over unintended acceleration and braking problems that have led to the recall of more than 8.5 million vehicles globally.

“We pursued growth over the speed at which we were able to develop our people and our organization, and we should sincerely be mindful of that,” Toyoda said in written testimony for a hearing scheduled for Wednesday.

Toyota’s recent safety problems revolve around sticky accelerators, accelerators that can be pinned down by loose floor mats and a braking glitch affecting its hybrid models.

But many lawmakers, some Toyota owners and safety experts fear Toyota’s current recalls do not cover all complaints of runaway acceleration and also want reforms at the National Highway Traffic Safety Administration.

Rhonda Smith, driver of a Toyota Lexus in a 2006 incident where her car reached 100 mph, told lawmakers on Tuesday she felt Toyota and NHTSA had dismissed her belief that the vehicle’s electronics were to blame.

“Shame on you, Toyota, for being so greedy. And shame on you, NHTSA, for not doing your job,” Smith, who at times was tearful, told the House Energy and Commerce Committee panel.

Toyota’s top-ranking U.S. executive, Jim Lentz, arrived for Tuesday’s hearing in a silver 2010 Toyota Highlander SUV, one of the vehicles subject to the sticky accelerator recall.

“We now understand that we must think differently when investigating complaints and communicate faster, better and more effectively with our customers and our regulators,” said Lentz, Toyota’s U.S. sales chief.

Under questioning, Lentz agreed that 70 percent of complaints about unintended acceleration remained unexplained. “That is probably fair to say,” he said. “There are many factors that lead to it.”

U.S. Transportation Secretary Ray LaHood said he would hold Toyoda to his assurance that the carmaker is working to address all safety issues.

MOST DIRECT APOLOGY

Toyoda, grandson of Toyota’s founder, is to testify on Wednesday before the House Oversight and Government Reform Committee.

The sprawling investigation into Toyota’s safety problems and the automaker’s response now includes a criminal probe by U.S. prosecutors and requests for information from the U.S. Securities and Exchange Commission.

In his written testimony, Toyoda apologized to the surviving family of Mark Saylor, an off-duty California Highway Patrol officer, who was killed along with three members of his family last August.

It was the most personal and direct apology so far from Toyoda, who has appeared uncomfortable with the media spotlight and initially resisted calls to testify before lawmakers.

The unintended acceleration problems with Toyota vehicles have been linked to at least five U.S. deaths, with 29 other fatality reports being examined by U.S. authorities.

Several lawmakers at Tuesday’s hearing criticized Toyota’s resistance to probing whether its electronic throttle systems can suffer from electromagnetic interference (EMI).

“Toyota’s leadership has been ambiguous about whether these two recalls fully account for and address the problem of sudden unintended acceleration,” said Rep. Bart Stupak, the Michigan Democrat who chairs the oversight and investigations subcommittee.

Henry Waxman, the California Democrat who chairs the full commerce committee, called for fundamental reforms to Toyota’s leadership and said reforming NHTSA would require legislation.

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“There is no evidence that Toyota or the government agency NHTSA took a serious look at the possibility that electronic defects could be causing the problem,” Waxman said.

He said Toyota did not initiate a study into possible electronic defects until two months ago and NHTSA does not have an electrical or software engineer on staff.

David Gilbert, a professor of auto technology at Southern Illinois University Carbondale, said he had found a possible flaw in the electronic throttle system on Toyota vehicles.

But Steve Buyer, a Republican from Indiana, said Gilbert’s financial ties to pending Toyota lawsuits undermined his objectivity.

Lentz said Toyota engineers in Japan had told him that there was no evidence of any flaw with the automaker’s electronic controls. Toyota has only begun working with an outside consultancy, Exponent, whose work was singled out for criticism as incomplete by Waxman.

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Several Republicans on the committee cautioned that Toyota should not be subject to an unfair grilling.

Texas Republican Michael Burgess said U.S. government ownership of General Motors posed an “inherent conflict of interest” in assessing Toyota.

The U.S. Treasury assumed a majority stake in GM last year in return for bailout money and bankruptcy financing.

PR DISASTER

Adding to the Japanese automaker’s deepening crisis, documents surfaced over the past two days which detail how Toyota beat back U.S. safety regulators’ efforts for a wider probe in 2007.

Aaron Bragman, an analyst at IHS Global Insight, said the situation looked likely to get worse this week for Toyota.

“From a public relations standpoint, this has been an unmitigated disaster from the start for Toyota, handled poorly by a team unfamiliar with major public relations catastrophes,” Bragman said.

Mike Jackson, chief executive of AutoNation Inc, was one of several hundred Toyota dealers and workers who came to Washington on Tuesday as part of a campaign organized by the automaker to help win back popular and political support.

“I’m certain that once the vehicles have been repaired and production has resumed that going into March and April, that (Toyota’s) sales will recover,” Jackson told Reuters Insider.

In the wake of Toyota’s massive recall, Consumers Union, the nonprofit publisher of Consumer Reports, issued a call on Tuesday for urgent changes to strengthen U.S. auto safety regulation.

It said that the U.S. safety regulatory system should be reformed to become more transparent and that the National Highway Traffic Safety Administration should have more funding and the ability to impose tougher sanctions.

Toyota’s U.S. shares were down 1.9 percent at $71.58 late on Tuesday afternoon on the New York Stock Exchange.