The Transport Ministry plans to issue orders to Mitsubishi Motors Corp. next month demanding that the firm make its operational procedures concerning vehicle recalls more transparent after it was revealed that defects had been concealed for decades, ministry officials said Wednesday.

According to the ministry, an automaker is required by law to inform the Transport Ministry of vehicle defects that pose serious safety or environmental dangers. The firm must then repair the faults free of charge.

It was revealed Tuesday, however, that MMC had for nearly 30 years hidden customer complaints and defects from authorities that would usually require notification.