The family of a man working on Tokyo's Olympic stadium who took his own life say that overwork was the cause of his death. His parents have petitioned the Japanese government to recognise his suicide as 'karoshi', the Japanese legal term for 'death by overwork.'

"We can confirm that the parents of a 23-year-old man who committed suicide have applied for workers' accident compensation," an official at the Labour Standards Inspection office said. He declined to give further details due to privacy concerns.

The construction worker, who began working on the stadium in December, clocked 200 hours of overtime a month before his body was found in April. "I'm taking today off," he told colleagues before he disappeared in March, a month before police discovered his body and the suicide note he had written.

"We were worried as he had such short sleeping hours," his parents told Japanese media through their attorney Hiroshi Kawahito. They said he would wake up at 4.30am and would not get home till after midnight. "We really don't want other people to die from overwork like our son," they said.

Every year hundreds of 'karoshi' death are recorded in Japan. A fifth of the Japanese workforce faces the risk of death from overwork, according to a 2016 survey by the Japanese government into the country's strenuous working culture.

Of Japanese companies polled, 23% said that some of their employees logged more than 80 hours of overtime. The report stated that on average 21% of Japanese employees work 49 hours or more each week.

Construction of the Tokyo's new National Stadium began in November 2016, after a year's delay following the rejection of the first design of the stadium. It is set to be completed in November 2019, in time for the Olympic Games that summer.

The organisers of the 2020 Tokyo Olympic Games said they were "saddened" by the news of the man's death. They promised "to take the utmost care to ensure there is no reoccurrence of such tragic events."