Toyota on Thursday admitted there was a design problem with the braking system in latest Prius but said it had redesigned the anti-lock system for cars produced since last month and would soon announce steps for those already on the road. The Japanese government called on the automaker to firmly investigate and address complaints.

"The design changes on the ABS were implemented in January," Hiroyuki Yokoyama, a Toyota managing officer in charge of quality control, told AFP.

"We, as a maker, want to take some sort of measures to explain to our customers and are studying it now. We'll make an announcement before long," added Yokoyama.

"The brakes are slow but if you continue to step on them, the car will stop," he told a hastily convened press conference held after the group announced quarterly earnings results.

US authorities have reported more than 100 complaints of brake problems on the Prius, while Toyota said it had received 77 complaints in Japan.

Toyota denied it had dragged its feet on revealing the problem, saying the initial reports of trouble were only received late last year.

"From around December, the number of complaints increased because of the icy weather," Yokoyama said.

He said when the ABS was in operation, there was a small delay switching from regenerative braking to the hydraulic brake.

"You can stop your car safely if you push the brake pedal strongly."

He did not say whether Toyota would issue a recall over the brake problem.

However, the Japanese government called on the automaker to firmly investigate and address the brake complaints.

Mizuho Fukushima, minister in charge of consumer affairs, met in Tokyo with Toyota managing officer Mitsuru Takada and told reporters after the meeting that she urged the automaker to investigate and report back on the issue, and called for measures to prevent the spread of uncertainty among Prius users.

''We want to coordinate with the Land, Infrastructure, Transport and Tourism Ministry and think of ways to deal with the matter,'' she told Kyodo News, indicating that the government would consider its response after Toyota reports on its investigation.

Toyota officials told Fukushima that their company determined there was no need to make the complaints public because the problem was a ''normal'' one, according to meeting participants.

Senior vice environment minister Issei Tajima expressed regrets about the problems reported with the Prius and urged Toyota ''to work toward recovering confidence by carrying out a thorough investigation.''

A Toyota GB spokesman said: "Toyota can confirm that there have been no reported problems in the UK or Europe with the braking performance of the current Prius."