The Fair Trade Commission is investigating Seven-Eleven Japan Co. for allegedly restricting franchise stores from discounting sales of boxed lunches and other food products close to their expiry dates, the company's owner said Friday.

It is the first time the antimonopoly watchdog has opened a full investigation into "member-store bullying" by the headquarters of a major convenience store chain since it announced new guidelines on the franchise system in 2002.

Lawyers representing the nation's largest convenience store chain told reporters they are "not aware of infringement," but explained that the sales instructors could tell franchise stores that bargain sales are "not favorable" because they may damage the chain's image of offering fresh produce and lead to competition with supermarkets.