MITSUBISHI Motors says it has found evidence its employees falsified fuel economy data for several models of vehicles.

The company says the inaccurate tests involved 157,000 of its own brand light eK wagon and eK Space light passenger cars and 468,000 Dayz and Dayz Roox vehicles produced for Nissan. None of the mentioned vehicles are sold in Australia but the company says it plans to investigate whether data was altered for vehicles sold overseas.

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

A local spokeswoman for Mitsubishi says while no local cars are affected the company was monitoring the situation.

“Taking into account the seriousness of this issue, MMC has advised it will also investigate products manufactured for overseas markets.

“This investigation will be conducted by a committee of experts operating independently of Mitsubishi Motors.

“In the meantime, MMAL will continue to monitor the situation closely,” she said.

The admission, which saw shares in the company plunge 15 per cent, is the latest in a series of scandals involving car companies understating or deliberately misleading consumers on fuel consumption and emissions.

Volkswagen has admitted to installing cheat devices on some vehicles to improve emissions results, while Kia and Hyundai were forced to pay fines in the United States after overstating fuel economy claims.

The revelations have put increasing pressure on regulators to take a greater role in testing vehicle emissions and fuel economy.

At the moment authorities trust the carmakers to perform a laboratory fuel economy test that is supposed to replicate real world driving.

But the makers have become expert at getting lower figures by deliberately tweaking cars for the test itself, rather than for real-world economy. They pump up tyres to get less resistance, disconnect alternators, use low friction oil and remove the spare tyre to reduce weight. Some have been known to test at high altitude for a better result.

As a result the fuel economy windscreen stickers on most vehicles are optimistic to say the least.

The Australian Automobile Association said earlier this year it would conduct independent real-world tests on 30 popular models over the next 18 months to highlight the flaws in the current system.