Mitsubishi Motors has admitted it falsified fuel economy test data to make emission levels look more favourable.
The company's president held a news conference today to apologise, saying the use of improper tests breached Japanese regulations.
Shares in Mitsubishi closed down more than 15 percent -- the stock's biggest one-day drop in nearly 12 years.
It's been reported the issue affected around 600,000 mini-vehicles produced under the brand.
Newshub.