Japan Post Insurance Co. has admitted mismanagement in connection with more than 90,000 insurance policies, the biggest scandal for the country's dominant postal group since its privatization in 2007.

The company on Wednesday said it has found about 22,000 cases in which customers were forced to make duplicate premium payments for both new and old, terminated insurance contracts between April 2016 and December 2018.

In addition, about 47,000 cases were tallied in which customers weren't covered despite having paid the premiums, and about 23,900 cases where the insurer refused to extend their contracts without sufficient reason, during the five-year period through this March.

Japan Post Insurance initially denied any wrongdoing, underscoring that customers consented to their contracts.

Mitsuhiko Uehira, president of the insurance arm of Japan Post Holdings Co., apologized at a news conference.

Kunio Yokoyama, president of Japan Post Co., the group's mail-delivery unit, which also sells insurance policies, said the cause of the misconduct might have been caused by staff attempting to meet their sales targets.

"Our sales targets did not fit with the times," Yokoyama said at the same news conference, referring to a tough business environment caused by the shrinking population and ultralow interest rates. "We'll strictly respond if any illegal activity is found."

The Financial Services Agency is considering ordering Japan Post Insurance to improve its operations, officials at the watchdog said.

The insurer said it will launch a third-party investigation a compensatory measures for customers, including the refund of overpaid premiums.