TOKYO - Mitsubishi Motors has admitted falsifying fuel economy data for more than 600,000 vehicles sold in Japan. Tyre pressure figures were falsified by employees to flatter mileage rates, the company said. Almost 470,000 vehicles that Mitsubishi made for Nissan were affected and the issue was uncovered after Nissan found inconsistencies. The announcement sent shares in Mitsubishi down more than 15% in Tokyo. Company bosses, including Mitsubishi Motors president Tetsuro Aikawa, bowed deeply at the start of a press conference on Wednesday afternoon in Tokyo. "The wrongdoing was intentional. It is clear the falsification was done to make the mileage look better. But why they would resort to fraud to do this is still unclear," he said. Although he was unaware of the irregularities, Mr Aikawa said: "I feel responsible." The issue was reported to Japan's transportation ministry and Nissan told dealers to stop selling the affected vehicles. Nissan was considering ways to help owners of the cars already sold. Mitsubishi, Japan's sixth-largest car maker, sold more than one million vehicles last year, but has less than 1% of the UK market. The company said it would investigate whether data were altered for vehicles sold overseas. It struggled for years to regain consumer trust after a defects scandal in the early 2000s that covered up problems such as failing brakes, faulty clutches and fuel tanks that fell off vehicles. The inaccurate tests involved 157,000 of its own brand light passenger cars and 468,000 vehicles produced for Nissan. Shares closed down 131 yen at 733 yen in Tokyo - their biggest one-day fall in nearly 12 years. This is the first time that a Japanese car maker has reported misconduct involving fuel economy tests. In 2014 South Korean car makers Hyundai and its affiliate, Kia, agreed to pay $350m in US penalties for overstating their vehicles' fuel economy ratings. They also resolved claims from car owners. Mitsubishi's announcement follows on from the Volkswagen's emissions scandal last year, in which it was found to have cheated diesel emissions tests in the United States and elsewhere. VW is recalling millions of cars worldwide as a result of the scandal and has set aside €6.7bn (£4.8bn) to cover costs. It resulted in the company posting its first quarterly loss for 15 years of €2.5bn in late October.(FA)