Japan one of the world's most rapidly ageing societies, passed a law today to prevent abuse of the elderly, one of the first steps taken by the government to tackle what experts say is a growing problem. 

Elder abuse is hardly unique to Japan, but the first public revelations last year of its existence were deeply disturbing to a society long so respectful of its senior citizens that there is even a national holiday in their honour. 

The new law, which comes into effect in April 2006, will protect the rights of the elderly by requiring those who discover abuse to inform local authorities, who then will be required to investigate each case in cooperation with the police. 

''At last, Japan is gaining some of the same standards as other nations around the world,'' said Soji Tanaka, a professor at Tokyo's Nihon University and one of Japan's leading experts on elder abuse. 

''I've been working towards this law for 14 years, until finally politicians began to listen,'' he added. 

According to the new law, ''abuse'' is defined as assault that could cause physical injury, verbal abuse, neglecting care, and wrongful management of the property of the elderly. 

Elder abuse, recognised as an issue in the United States and some European countries as early as the 1980s, typically crosses all economic lines and ranges from physical and psychological abuse to neglect and economic abuse, such as appropriating savings and pensions. Japan is no different. 

But it was not until April last year that Japan released its first survey on elder abuse, finding 1,991 cases. 

While this number is small compared to the United States, which has twice Japan's population and where an estimated 551,000 cases were noted in a late-1990s report, experts say the actual number may be as high as 10,000 -- and that abuse is increasing. 

One unique aspect of elder abuse in Japan is the relatively high number of seniors who live with their grown children, the result of traditions that have long said caring for aged parents is a filial duty, especially for elder sons. 

Given that support services for such caregivers are rudimentary at best, experts were not surprised that the survey found that 32 per cent of abusers were sons and 21 per cent their wives -- the ones who often end up doing the most care. 

Some, though, say more cases have simply come to light since 2000 because a new law increasing the number of home care workers allowed more people into private homes. 

Tanaka at Nihon University said that giving power to local governments to investigate the issue was a huge step forward since it would allow authorities to investigate allegations of abuse within households, traditionally sacrosanct in Japan. 

That attitude has hampered authorities in tackling child abuse and domestic violence, but is particularly acute in dealing with the elderly, who often cannot leave their homes. 

The law is still only the first step, Tanaka warned, noting that few governments had guidelines to implement it. 

''This means that responses to abuse complaints could be delayed, in a worst-case scenario actually allowing some elderly abuse victims to die,'' he said. ''Just having the law in place is not enough.''