An independent, third party investigation commissioned by the automaker revealed safety tests and other procedures on a large number of new models had been widely and systematically falsified by company staff and suppliers over three decades.

Late in January, the company was allowed to resume production and sales of five models, the Daihatsu Grand Max, Toyota Town Ace Van, Mazda Bongo van, Toyota ProBox and Mazda Familia Van, as they were found to “comply with the standards of the Road Transport Vehicle Act”. The first three models were produced in Indonesia by PT Astra Daihatsu Motor and shipped assembled to Japan and other markets in the region.

Earlier this week, Daihatsu said it had resumed production at its head office plant in Ikeda in Osaka prefecture, with all four domestic assembly plants now back on line.

The company said it would increase production to make up for lost output and fulfil back orders which have resulted from the suspensions.

Last month, parent Toyota Motor announced a series of measures to help prevent these problems reoccurring, including increasing its direct control of Daihatsu new vehicle development operations with the subsidiary in future to be “commissioned” to handle actual new product development.

Toyota said the restructuring was aimed at “thoroughly preventing the recurrence of procedural irregularities at Daihatsu” and to better leverage Daihatsu's strengthens in the small car segment.