The Transport Ministry has received some 80 complaints in February about malfunctions in the brake system of the latest model of the flagship Prius, the Tokyo Shimbun reported without quoting sources.
Five of them were actual crashes in which the drivers claimed the brakes did not work properly, the daily said, adding that the ministry would urge the company to launch an investigation.
It was not possible to immediately confirm the report.
Toyota said Friday that it was still considering whether to recall the Prius, a day after confirming the fuel-sipping car had a design flaw.
The company said it had redesigned the anti-lock braking system -- designed to prevent skidding -- for the latest version of its Prius produced since last month and would soon announce steps for those already on the road.
Major Japanese newspapers lashed out at Toyota's slow response to safety problems with its cars and warned the fiasco could hurt the country's hard-won reputation for trustworthy technology.
Company president Akio Toyoda said Friday he was "deeply sorry" for the string of quality issues that has tarnished the group's reputation and triggered a class action lawsuit in the United States.
But the Nikkei business daily said in an editorial: "Words alone cannot settle the situation. Toyota represents Japan and its shaking could lead to a loss of trust for the entire Japan brand."
The Asahi Shimbun decried Toyota's response to the troubles as "utterly slow," adding that "the world is watching how Toyota will show its humility by using the series of troubles as lessons for the production of safe cars."
The Yomiuri Shimbun said: "There is no denying Toyota was over-confident about its models' high-tech equipment and treated users' complaints lightly.
"Failure to deal properly with the current fiasco could deal a blow to the international trust in Japan's manufacturing technology," the best-selling daily said in an editorial.
"We hope Toyota humbly accepts the criticism levelled against it and will do all it can to ensure the safety and high quality of its vehicles," it concluded.
Toyota, staring at a two-billion-dollar bill from the recall of more than eight million vehicles around the world, was facing "a moment of crisis," admitted Toyoda, grandson of the company's founder.
Toyota, which dethroned General Motors in 2008 as the world's biggest automaker, is reeling from a series of complaints about problems ranging from unintended acceleration to brake failure.
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