No one knows the true scale of the problem because despite more than a decade of appeals from senior police officers and recommendations by the European Union, the Government has yet to set up a central register of runaways.
Instead police forces, along with concerned relatives and friends, frequently have to rely on the services of volunteers at the Missing Persons Bureau - a charity with extremely limited resources that is based in donated offices above a supermarket in a London suburb.
The problem of tracing and identifying missing people has been highlighted with the discovery of seven bodies at 25 Cromwell Street.
Gloucestershire Police and the bureau are searching through all their missing persons files dating back to the 1960s looking for people who have disappeared from the region. Chris Dray, from the bureau, yesterday visited No 25 to try to help police identity the bodies.
The gruesome finds illustrate how people can 'disappear' without anyone noticing. Neither of the two identified bodies - Heather West, who was 16 years old when she disappeared in 1987, or Shirley Robinson, 18 - was reported missing.
Sophie Woodforde, spokeswoman for the Missing Persons Bureau, said this was not unusual. 'If someone reports a missing person who is over 18 years old and not considered vulnerable the police, whose resources are limited, would not necessarily put them on a missing list.
'It is also not uncommon for family members to lose contact with each other and fail to notice when someone apparently vanishes. Others will leave their family and mistakenly think they are unwanted and unloved.'
Of the 250,000 on the bureau's files, many are children. A recent survey by a children's organisation estimated that 98,000 young people were missing.
They leave because of problems at home, difficulties at school, and the influence of older boy and girlfriends.
Figures from the Metropolitan Police show that in the year ending March 1993, of the 30,475 people reported as missing, more than 5,700 were boys and girls aged 13 and under; 71 are still missing. In the 14-to-18 age group there were more than 16,000 missing people, of which 171 have still not been located. There were more than 8,500 missing adults, of which 316 have not been traced. The force has an additional 882 missing persons from previous years.
Middle-aged people are prone to running away because of pressures from work. Often they have been made redundant and cannot face their families, or they suffer from debts, alcoholism, broken relationships, drug abuse and depression.
Among the elderly, mental problems are a key factor. Some psychiatrists believe going missing is an alternative to committing suicide.
The majority of people will be located within a few days. In London about half returned on their own accord; a quarter were found after police inquiries and publicity; 4 per cent were caught committing a crime; 1 per cent died; and about 20 per cent were identified from other sources such as friends and benefit agencies.
A clearer picture should emerge in the next few years as the Home Office plans to use the new Police National Computer to set up the first national service.
This follows a recommendation in 1979 from the Council of Europe that all European countries should have a national missing persons bureau. Five years later, the Association of Chief Police Officers made a similar recommendation.