The Transport Ministry said the figure came from its own mileage tests to look into the cheating by the Japanese automaker on its minicar models, tiny cars eligible for tax breaks in Japan and reputed to deliver very good mileage.
Tokyo-based Mitsubishi Motors acknowledged recently it had systematically inflated mileage for eK minicar models, as well as some other models. But it has said it did not lie on mileage on models sold abroad.
The ministry said the mileage Mitsubishi initially gave was off by an average of 11 per cent and up to 16 per cent. That was close to what Mitsubishi had given when it acknowledged its wrongdoing and released new estimates. Mitsubishi is under orders to submit fixed data to the government.
"We find it deplorable that the actual mileage was so much lower," Minister Keiichi Ishii told reporters.
It will take a 50 billion yen (USD 913 million) charge to cover the mileage-rigging expenses, including for the eK minicar models sold in Japan since 2013, and also for those sold under the Nissan badge.
Mitsubishi's latest scandal follows its massive and systematic cover-up of defects that surfaced in the early 2000s, which had spanned decades. The automaker has repeatedly promised to fix its ethical standards. The company's president has stepped down to take responsibility for the new scandal.