"The overall value of internal trading dropped as the FTC raised the minimum ceiling last year, but the percentage went up," the watchdog said in a release. "The FTC will keep monitoring such practices and take stern action."

The current law forbids inter-affiliate trading within a business group whose owner and family hold more than 30 percent of the shares in an affiliate. Such trading is blamed for allowing owner families to easily net large profits by having subsidiaries award lucrative contracts to each other, undermining the principle of fair competition.

Hyundai Motor Group, South Korea's second-largest conglomerate by assets, reported the largest intra-affiliate deals, with a value of 30.3 trillion won, followed by SK Group with 29.4 trillion won and Samsung Group with 21.1 trillion won.

At the same time, such transactions by leading steelmaker POSCO accounted for 38.5 percent of the total, while Hyundai Heavy Industries came next with 37.4 percent and SK Group with 36.6 percent.

The latest data also showed that 849, or 83.2 percent, of the 1,021 affiliates belonging to the 27 conglomerates engaged in intra-group trading of some sort. Of these, 390 affiliated firms, or 38.2 percent of the total, reported inside deals making up more than 30 percent of their revenue. (Yonhap)