Seven-Eleven Japan Co. has sent a formal warning to a franchise owner who filed a request to temporarily shorten operating hours due to a shortage of labor, the owner said Friday.

The leading convenience store chain has been under scrutiny over its stance toward franchise owners who are having difficulty finding help. The latest development came just months after the company pledged to review its 24-hour operating policy and respond more flexibly to the needs of each outlet.

The franchise owner in Gunma Prefecture received the letter Friday from Seven-Eleven Japan President Fumihiko Nagamatsu, who warned of “a serious violation.”

The owner had asked permission to close his outlet for the five-hour period ending at 4 a.m., only on July 12.

The company said franchise owners are required to have an agreement with the chain if they are to shorten hours, and that in the case in question, the two sides have yet to begin talks.

“I was surprised that (the company) threatened me with the word ‘warn,’” the owner said.

Seven-Eleven has been mired in controversy over its 24-hour operating policy after a franchise owner in Higashiosaka, Osaka Prefecture, cut business hours at his store in February over a labor shortage without approval from the parent firm.

The trade and industry ministry has since urged convenience store chains to draw up an action plan to address problems linked to operating hours. Many store owners have been struggling to secure labor amid the rapidly graying population and are increasingly relying on foreign part-time workers to fill shifts.