Transactions among affiliates of South Korea's large conglomerates edged down in 2015 as they heeded growing criticism over unfair business practices, the antitrust watchdog said Thursday.

According to the Fair Trade Commission, cross-affiliate deals accounted for 12.4 percent of all business contracts inked by South Korea's 48 largest conglomerates this year. The value of the deals totaled 181.1 trillion won ($153.1 billion), down 400 billion won from the year before.

"The numbers are still high, but since peaking in 2011, conglomerates have been taking steps to reduce internal trading," the FTC said. "Both voluntary measures and government pressure are nudging companies to curtail such transactions."

The corporate regulator keeps track of intra-group trading because such arrangements award lucrative contracts with favorable terms to companies within the business group.

This effectively blocks out other companies from the competition and distorts fair market rules. In 2013, the National Assembly passed a law that bans intra-group trading if the shares held by the conglomerates' owners or family members in an affiliate exceed a set limit.

By conglomerate, SK Group's cross-affiliate transactions accounted for 28.9 percent of this year's total, followed by steelmaker POSCO and Hyundai Motor Group at 19.4 percent and 18.8 percent, respectively.

In terms of value, SK again led the pack with 47.7 trillion won, followed by 31.1 trillion won for Hyundai Motor and 25.3 trillion won for Samsung, the country's largest family-run conglomerate.

The latest data also showed that of the 1,347 affiliates belonging to the 48 conglomerates, 1,129, or 83.8 percent, engaged in intra-group trading. Of these, 503 or 37.3 percent of the total, reported inside deals making up more than 30 percent of their revenue. (Yonhap)