Japanese carmaker Nissan has said it has uncovered falsifying emissions and fuel economy data at most of its factories in Japan.

The company said it had uncovered the falsified data during voluntary testing after the Japanese Government found that its inspection process was faulty.

It said the data had been deliberately "altered" - although it did not say how many cars had been affected.

The “misconduct” related to emissions and measurements in final vehicle inspections at most of its factories in Japan. 

Last September, Nissan admitted unqualified workers had been carrying out final inspections at the end of productions lines.

It said the illegal inspections may bate back as far as 1979 at its plant in Tochigi.

The announcement triggered a domestic recall of 1.2 million vehicles.

Shares in Nissan tumbled by about 5% as soon as the company announced it would be issuing an explanation about its emissions measurement processes.