More than 250,000 people under the age of 25 in England and Wales could be classified as homeless, a BBC investigation has concluded.
Teenagers can leave home after rows, campaigners say
Many left home as teenagers after rows with their parents and now live in poor quality hostels or on friends' sofas - and are not included in official data.
Campaigners working with vulnerable teenagers have called for more family mediation services.
Government measures help the under-18s who leave home find accommodation.
Under the Homelessness Act, local authorities are obliged to provide them with advice and temporary housing.
But according to charities working with the homeless, many youths never claim housing benefits or are excluded from accessing services in the first place.
The 250,000 figure has been drawn from estimates supplied by charities dealing with the homeless, housing benefit numbers and local authority data.
The housing and homelessness charity Shelter said it has long been calling on the government to abolish a restriction that caps the amount of housing benefit the under 25s can receive.
"By ending this restriction, the government will be taking an important step towards addressing the problem of homelessness and giving young people fair access to decent, affordable housing and a brighter future," said Martha Hannan, head of campaigns at Shelter.
Children's charity NCH said one in five homeless people are care leavers and called for more resources to be put into early intervention services to help children stay with their families.