Tadashi Ishii has resigned from his role as President and chief executive of Dentsu ©Getty Images

Tadashi Ishii has resigned from his role as President and chief executive of Dentsu after an employee of the marketing giants committed suicide on Christmas Day last year due to being overworked.

Ishii told a news conference in Tokyo that he will step down from his position at the helm of the company, who are the marketing agency for the Tokyo 2020 Organising Committee and other bodies such as the International Association of Athletics Federations (IAAF), in January.

It comes after Matsuri Takahashi, who had been working for the world’s fifth-largest advertising agency holding group for eight months, committed suicide on December 25, 2015.

Ishii’s announcement followed the Tokyo Labour Bureau referring the company and its officials to prosecutors on suspicion of forcing Takahashi to work and under report illegally long hours.

His replacement will be chosen at a board meeting on an unspecified date in January.

“We deeply regret failing to prevent the overwork of our new recruit,” Ishii said.

“I offer my sincere apology.

“Although we took various countermeasures, the issue of overwork has not been improved.

“I will take full responsibility.”

Tadashi Ishii says he takes full responsibility for the suicide of an employee ©Getty Images
Tadashi Ishii says he takes full responsibility for the suicide of an employee ©Getty Images

Ishii has reportedly been allowed to apologise to the family of Takahashi following the tragedy.

Her mother, 53-year-old Yukimi, urged the company to make sure it implements efforts to end long working hours so there will not be "a victim like Matsuri in the future”.

According to the Asahi newspaper, Takahashi had put in 105 hours of overtime from the course of a month from October 9.

It is claimed Takahashi’s supervisor broke labour laws in Japan by forcing her and another employee to work long hours between October and December, before she tragically took her own life on Christmas Day.

Dentsu lowered the hours of overtime its employees are allowed to undertake from 70 down to 65 last month.

The labour standards inspection office in Tokyo confirmed Takahashi’s death was a case of karoshi, which is Japanese for death by overwork.

She was suffering from depression prior to her suicide, which was exasperated by her rise in overtime hours from 40 to 100.

According to the Japan Times, a lawyer for the family said Takakshi had died after jumping from the upper floor of a company dormitory.

“It cannot be denied that this was a case of power harassment, given the fact that she lacked experience in the business,” Denstu vice-president Shoichi Nakamoto said while denying the company’s conduct was illegal.