Mitsubishi Motors has announced its president, Tetsuro Aikawa, will step down in the wake of the company's test-fixing scandal.

The Japanese carmaker has already admitted that it has been falsifying fuel efficiency tests for decades.

After Mitsubishi's share price slumped by more than 50%, fellow carmaker Nissan moved in to take a controlling stake in Mitsubishi.

In April, Mitsubishi Motors admitted it had rigged tests for the past 25 years.

Regulations changed in 1991 to better reflect stop-start urban driving, but Mitsubishi failed to heed the change.

Meanwhile, fellow Japanese carmaker Suzuki has said it has found "discrepancies" in its fuel and emissions testing, but denies cheating.

The company said its testing method for 16 models was not in line with official regulations, but it insisted that new tests showed no need to amend the data.

Penalties loom

Mileage fraud breaks Japan's fuel efficiency laws. It is unclear what penalties Mitsubishi might face, because of uncertainties about the outcome of further investigations.

Aikawa took on the role of Mitsubishi's president and chief operating officer in June 2015.

Before the scandal, Mitsubishi Motors was the sixth biggest carmaker in Japan and number 16 worldwide.

Annual car production currently stands at 1,218,853 vehicles.

Carmakers in the spotlight

Volkswagen has admitted to cheating emissions tests in the US. Authorities found the German carmaker was installing a cheating software in its diesel vehicles that could detect when the cars were being tested and would change carbon dioxide emission levels accordingly to improve the results.

Mitsubishi Motors has admitted it had falsified fuel economy data for the past 25 years. Breaking Japanese test rules meant the carmaker was able to advertise its vehicles as being more fuel efficient than they actually were.

Suzuki has admitted it has found "discrepancies" in its fuel and emissions testing but denies cheating. The company said its testing method for 16 models was not in line with official regulations, but it insisted that new tests showed no need to amend the data.

Nissan has been accused of having some of its UK-built Qashqais fitted with so-called emissions defeat devices. The company has denied the allegations.