The graft scandals involving the union of GM Korea show how corrupt some of the nation’s large unions are. It should serve as a reminder that we cannot eradicate labor corruption without reining in unions’ power and interference with management decisions like staff recruitment.

The latest case at the local unit of the U.S. carmaker General Motors started with an investigation into bribery allegations over the company’s purchase of gifts for employees on major holidays like Chuseok and Seollal and annual sporting events.

Altogether six from the company -- two executives and four union leaders -- were indicted for receiving kickbacks worth from 30 million won ($25,300) to 110 million won from suppliers of the gifts.

Because union members account for a large majority of employees, company officials usually work in cooperation with union leaders on selecting such gifts. 

Their collaboration -- and conspiracy -- was not limited to purchases of gifts. Prosecutors in Incheon said they were looking into suspicions that company executives and union leaders received kickbacks for giving favors to job seekers. 

They said company officials and union leaders are suspected of receiving tens of millions of won from each of the people the company hired as full-time workers. The suspects allegedly took advantage of a special employment track for contract-based workers from small suppliers. Workers who have stayed with small firms for one to two years are given chances to apply for full-time, permanent jobs at GM.

Prosecutors said whistle-blowers told them the practice started about 10 years ago and that the total amount of kickbacks stands as high as 100 million won. Prosecutors said they were tracking down financial transactions of suspects.

It is not the first time that unions of major carmakers have been implicated in money-for-jobs scandals. The most prominent cases involved Kia Motors in the southwestern city of Gwangju, where similar scandals erupted twice -- in 2005 and 2014.

The GM Korea scandal shows that all the concerned parties failed to learn lessons from the Kia cases. The most urgent task is to get to the bottom of the case and punish anyone and everyone who is responsible for the detestable acts. Also, measures should be taken to rein in the power of unions and keep them away from recruitment, purchasing and other management affairs.