Mitsubishi Motors Corp. said it falsified fuel economy test data to make emissions levels look more favourable, and its shares slumped more than 15 per cent, wiping $1.2 billion from its market value yesterday.

Tetsuro Aikawa, president of Japan’s sixth-largest automaker by market value, bowed in apology at a news conference in Tokyo for what is the biggest scandal at Mitsubishi Motors since a defect cover-up over a decade ago.

Test manipulation involved 625,000 vehicles

In 2000, Mitsubishi Motors revealed that it covered up safety records and customer complaints. Four years later it admitted to broader problems going back decades. It was Japan’s worst automotive recall scandal at the time.

The company said yesterday the test manipulation involved 625,000 vehicles produced since mid-2013. These include its eK mini-wagon as well as 468,000 similar cars it made for Nissan Motor. It said it would stop making and selling those cars, and has set up an independent panel to investigate the issue.

Mitsubishi Motors sold just over one million cars last year.

Mitsubishi Motors is the first Japanese automaker to report misconduct involving fuel economy tests since Volkswagen was discovered last year to have cheated diesel emissions tests.

South Korean car makers Hyundai Motor Co. and affiliate Kia Motors Corp. in 2014 agreed to pay $350 million in penalties to the US government for overstating their vehicles’ fuel economy ratings. They also resolved claims from car owners.