The nation's antitrust regulator will file a complaint with the prosecution against the truckers' union for obstructing its on-site investigation.

According to the Fair Trade Commission(FTC) on Wednesday, it plans to accuse the Cargo Truckers Solidarity union of deliberately disrupting the regulator's three rounds of on-site probe last month.

At the time, the FTC was looking into possible violations by the truckers' union, such as forcing people to join the strike or disrupting delivery operations.

The FTC claims the union denied its investigators entry. Under the law, obstructing the investigation by the FTC officials can result in imprisonment of up to three years or a maximum fine of 200 million won.

The union, which argues that it is a labor union not subject to FTC regulations, protested the latest move, accusing the regulator of "targeted oppression."

The government says the organization was established by individual truckers, each an individual business entity, and is not authorized as a labor union.