The number of elderly people caught shoplifting in Japan's capital city has outstripped that of teenagers for the first time since records began, a report said.

A quarter of the people arrested on suspicion of the crime in Tokyo last year were at least 65 years old, figures showed, amid warnings of increasing isolation in the age group.

"Even though the total number of arrests for shoplifting has been declining, the ratio of elderly people are on the rise," a Tokyo Metropolitan Police spokesman said.

"Our survey shows that elderly shoplifters tend to be lonely, having no one to talk to, and having no hobby to enjoy," he said.

Statistics showed 3,321 people aged 65 or older were arrested for shoplifting, accounting for 24.5 percent of the total, while those aged 19 or younger made up 23.6 percent, with 3,195 individual arrests. Both figures are slightly down in absolute terms from 2011, the spokesman said.

It was the first time since comparable data had been collected that the elderly made up a higher proportion of suspected thieves, the Mainichi Shimbun newspaper reported.

Around a quarter of Japan's 128 million population is aged 65 or older, and the country has a far-below replacement birthrate of an average 1.39 children for every woman.

There are regular reports of bodies lying unfound for weeks or even months after a single, elderly person has died alone. Commentators say the phenomenon is a result of the fraying of familial ties as Japan has modernised.

A government survey last week found 3.5 million elderly women and 1.4 million elderly men live alone.