Nissan Motor reportedly has said sales of new passenger vehicles in Japan probably halved in October - compared with a year ago - after the discovery of flawed final inspection procedures at its domestic plants resulted in some production being suspended.

Last month, the Japanese Ministry of Land, Infrastructure and Transportation (MLIT) said Nissan's final vehicle inspections were carried out by technicians not properly registered to perform those duties under the automaker's own processes.

On 19 October, Nissan said it would suspend vehicle production for the Japanese market at all Nissan and Nissan Shatai plants in Japan.

Though Nissan had taken corrective action by 20 September, by 18 October, the investigation team (led by a third party) discovered that, at its Oppama, Tochigi and the Nissan Kyushu plants, certain parts of the final inspection process were still being carried out by technicians not properly registered to perform those duties for vehicles for the Japan market.

"Nissan regrets any inconvenience and concern this has caused to its valued customers and other stakeholders in Japan," the automaker said in a statement at the time.

The discoveries prompted it to recall 1.2m vehicles, including all passenger cars it produced for sale in Japan over the past three years.

The plants would resume production once final inspection procedures complied with transport ministry requirements and the regulator had approved the measures, a Nissan spokesman told Reuters this week.

The automaker had completed changes at one assembly plant and expected similar work at five other plants to be done by the end of the week, he added.

Tightened procedures would mean only certified inspectors would be allowed into the final inspection area, and there would be regular checks that inspections were carried out properly, the Reuters report added.