Mitsubishi Motors cheated on fuel-efficiency testing for almost every model it sold in Japan in the last 25 years, a report said on Wednesday, fuelling questions about the size of a scandal that has plunged the automaker into crisis.

Citing unnamed company sources, Japan's Asahi newspaper said dozens of models sold in Japan have been affected since 1991, including sedans and sports utility vehicles (SUVs) such as the popular Pajero model.

The Asahi also said re-testing by the firm had found it overstated the fuel economy of some vehicles by more than 15 percent.

The company is reeling after it admitted last month that it had been using improper testing for years, and that unnamed employees manipulated data to make some of its cars seem more fuel-efficient than they were in reality. 

So far, Mitsubishi has confirmed that four models and over 600,000 vehicles -- all sold in Japan -- were involved in the cheating scandal, warning the number of cars affected would likely rise.
In response to the report, a Mitsubishi spokesman said the firm had already made clear the number of models affected would widen.

"We've already announced what's written here -- there is nothing new," he said, referring to the Asahi story.

But the new report is likely to stir speculation that the misconduct stretched to vehicles sold overseas and inflate the size of the crisis. Mitsubishi sold about one million vehicles globally last year.

The maker of the Outlander sport utility vehicle is scheduled to hold a press briefing later Wednesday after it submits a report on its internal investigation to the transport ministry.

Mitsubishi has said it could not make financial forecasts for the current fiscal year in light of the potential damage from the scandal, including the possibility of big fines, lawsuits and compensation costs.

The company's Tokyo-listed shares rose 2.27 percent at 495 yen. 

Investors had lopped more than 40 percent off Mitsubishi's shares in the wake of the automaker's admission last month.

Source: AFP