A recent inspection by the government has again found fake quality certificates for parts used in the country's nuclear power plants, the energy ministry said Tuesday.

The inspection by its own auditor has found seven fabricated certificates for five different kinds of parts from four suppliers, according to the Ministry of Trade, Industry and Energy. It said that the parts are directly related to the safety of nuclear reactors.

"They were not key parts under the tech-specification of the Nuclear Safety and Security Commission that would have limited the operation of nuclear reactors," the ministry said, adding the parts can be replaced without halting the reactors.

The latest discovery follows a major scandal in May 2013 when an investigation by the nuclear safety commission found massive amounts of substandard control cables supplied to three nuclear reactors under fabricated certificates, leading to their immediate shutdown.  They have resumed operation after months of special maintenance to replace all the parts.

Nuclear reactors provide about 30 percent of the country's electricity.

The ministry said the four companies implicated in the recent cases will face criminal and damage lawsuits.

The inspection also found that six state-designated certifiers, including the Korea Testing Laboratory and Korea Testing & Research Institute, failed to conduct adequate tests before issuing quality certificates.

Certifiers skipped the required double testing and fabricated the test results, the ministry said.

The six certifiers will face business suspension for up to three months, it said.

They include Korea Testing Certification, Korea Conformity Laboratories, Korea Apparel Testing & Research Institute and FITI Testing & Research Institute. (Yonhap)