For the second time in as many weeks, Mitsubishi Motors has admitted to manipulating data.

Last week, it was revealed that the company had falsified fuel economy data for four "minicar" models sold only in Japan. And this week, another scandal has surfaced with the motor group confessing that it has used fuel consumption tests that broke Japanese rules for the past 25 years.

Mitsubishi failed to abide by regulations which were introduced in 1991 in order to better reflect the stop-start aspect of urban driving.  

The executive vice-president of Mitsubishi said that he regrets that the company did not make the crucial switch, while the president Tetsuro Aikawa, said an inquiry led by three external lawyers had been opened:

"We don't know the whole picture and we are in the process of trying to determine that. I feel a great responsibility."

Mitsubishis' woes were compounded further when it transpired that shares fell by another 10% on Tuesday, bringing the slide since the scandal errupted to almost 50%.

It is also possible, that many more models, in addition to the four minicars, may have used fuel tests that did not comply with the regulations.

Mitsubishi has stopped making and selling all four models.

The company had previously vowed to come clean after a huge scandal emerged 15 years ago in relation to a systematic cover-up of vehicle defects.