Mitsubishi Motors says its employees intentionally falsified fuel mileage test data for several models of vehicles.

The Tokyo-based carmaker said that the inaccurate tests involved 157,000 of its own-brand eK wagon and eK Space light passenger cars, and 468,000 Dayz Roox vehicles produced for Nissan Motor.

The problem was found after Nissan pointed out inconsistencies in data, the company said. Mitsubishi conducted an internal probe and found that tyre pressure data was falsified to make mileage appear better than it actually was.

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“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,” company president Tetsuro Aikawa told reporters on Wednesday.

He and other company executives bowed in apology.

Aikawa said that although he was unaware the irregularities were happening, “I feel responsible”.

The company said it would investigate whether data were altered for vehicles sold overseas.

Mitsubishi Motors struggled for years to win back consumer trust after an car defects scandal in the early 2000s over cover-ups of problems such as failing brakes, faulty clutches and fuel tanks prone to falling off dating back to the 1970s.

The company’s shares plunged 15.2 per cent on Wednesday.

-AAP