Old people in Japan should kill themselves to avoid burdening the state, a professor at Yale University has said.

Dr Yusuke Narita, an assistant professor of economics, has also suggested that euthanasia be made compulsory.

Last year, official statistics in Japan revealed that the over-75s accounted for 15 per cent of the country’s population for the first time. Those over 65 account for 29.1 per cent of the total, making the Japanese population the oldest in the world.

“I feel like the only solution is pretty clear,” said Narita, 37.

“In the end, isn’t it mass suicide and mass ‘seppuku’ of the elderly?” he said, referring to the act of disembowelment — more usually known in the West as hara-kiri — employed by dishonoured Samurai in the late 19th century.

Dr Narita told The New York Times his comments had been taken out of context, adding that they related to demands for older people in leadership positions to make way for the younger generation.

He said his primary concern was how old people dominated positions of influence in Japanese society.

The references to “mass suicide” and “mass seppuku” touched a raw nerve in a country which honoured kamikaze pilots during World War II.

Dr Narita insisted his remarks about mass suicide were a metaphor.

“I should have been more careful about their potential negative connotations,” he said.

“After some self-reflection, I stopped using the words last year.”

His remarks triggered an angry backlash in the media. Masato Fujisaki, a columnist, wrote in Newsweek Japan that Dr Narita’s fans are people “who think that old people should just die already and social welfare should be cut”.

Others fear he is encouraging views that have started to gain currency in Japan where deference for the older generation is waning. Dr Narita is yet to reply to a request for comment.

The Daily Telegraph, London