Failures by two councils led to a homeless 16-year-old boy being forced to spend nine months living in a tent and having to sell his belongings to survive, an inquiry has found.
Kent County Council and Dover District Council have been criticised by local government ombudsman Anne Seex for their "inexcusable" handling of the teenager's case.
She said the failures of the two local authorities could have "tipped him into a spiral of drug use and crime" and caused him physical and mental ill-health.
The investigation found he spent nine months sleeping in a tent, sometimes in snowy conditions, in various parts of rural Kent, or on friends' sofas.
He sold or gave away most of his possessions to pay friends who let him stay.
His tent was vandalised, his feet were often wet, and he lost weight and developed a chest infection.
In her report issued today, Ms Seex said Kent County Council failed to assess the "remarkably determined and resilient" boy, referred to only as "J", as a child in need and accommodate him.
Dover District Council failed to accept him as homeless and provide suitable temporary accommodation or contact Kent children's services about him.
Ms Seex said: "These failures are inexcusable.
"They happened after important court rulings had clarified the roles and responsibilities that housing authorities and children's services authorities have to homeless children of 16 and 17."
She added: "J was remarkably determined and resilient in the face of crushingly difficult circumstances and was well supported by the youth centre.
"The failures of the two councils could have easily tipped him into a spiral of drug use and crime."
The report said the boy became homeless at 16. As a younger teenager, he had been taken into care by Kent County Council and placed with foster parents.
He returned to his mother but she told him to leave when he objected to her relationship with a drug user. He applied to Dover District Council for housing but was turned away.
A youth centre manager told Kent children's services about the boy but those contacts were not recorded and for six months the services did nothing, the report added.
Dover would not accept him as homeless but offered him bed and breakfast, registered him for housing and offered him a one-bedroom flat.
But the boy rejected the offers because he did not want to be housed in areas where he would be tempted into drugs and crime.
After pressure from the neighbourhood police officer, the Youth Offending Service, the YMCA and a local drug and alcohol service, Dover offered him another flat which he accepted.
Dover demanded an adult guarantor for the tenancy but for six weeks it refused to accept a £1,000 guarantee from Kent children's services.
The ombudsman was critical of Dover's demands about a guarantee, describing them as "obdurate".
The report said: "Throughout this time, J was still a child.
"He spent nine months sleeping in a tent, sometimes in snow, or on friends' sofas. His tent was vandalised and his physical and mental health suffered.
"His feet were frequently wet, he had back pain and lost a lot of weight, and developed a chest infection."
The ombudsman found maladministration because Kent County Council failed to respond to being told about the boy and failed to fulfil its duties to him under the Children Act 1989.
Dover District Council failed in its duties under the Housing Act 1996 and failed to follow its joint protocol with Kent.
The ombudsman recommended that the councils apologise in writing to the boy and each pay him £5,500.
Kent County Council offered an apology as the housing and homelessness charity Shelter, which helped the boy bring his case to the ombudsman, said many 16 and 17-year-olds are not getting the support they need when they ask local authorities for help.
Jenny Whittle, Kent County Council's cabinet member for specialist children's services, said: "There is no mistaking that the system as a whole failed.
"We accept our role in that and offer our sincerest apologies to this young man.
"The county council has largely implemented the improvements recommended by the ombudsman, and the way we deal with homeless young people, aged 16 and 17, changed substantially following new Government guidance, published in April 2010.
"On the particular point of reviewing arrangements for receiving and recording telephone calls to its children's services, Kent County Council has already introduced a central duty team, led by social workers, to make sure referrals are dealt with in an efficient and timely way.
"Kent County Council and its partners are working together more closely to protect and support vulnerable children, young people and their families.
"While this in no way makes up for this young man's experience, I hope it offers some reassurance that lessons have been learned and procedures changed."
Shelter chief executive Campbell Robb said: "Despite several court rulings in recent years confirming local authorities' responsibilities to homeless teenagers, many homeless 16 and 17-year-olds are still not getting the support they need and are entitled to when they approach them for help.
"Today's report highlights how vital it is that local authorities comply with their legal responsibility to implement effective joint protocols for assisting homeless 16 and 17-year-olds.
"Without this, vulnerable young people can end up falling through the cracks between children's services and housing departments, leaving them out on the streets.
"Shelter's children's legal service and Freshfields Bruckhaus Deringer LLP, acting pro bono, helped the young person in this case to put forward their complaint so that other homeless young people would not be let down in the same way.
"We hope those efforts and the ombudsman's decision today mean that proper and timely support will be provided by all local authorities in the future."
Dover District Council apologised for its handling of the case and said recommendations by the ombudsman are already in place to prevent a repeat.
A council spokesman said: "The case in question happened in January 2009 and the council immediately made procedural improvements for dealing with homeless young people.
"The needs of vulnerable young people are addressed in the council's adopted youth homelessness strategy.
"We appointed a housing options adviser (young people) early in 2009 and also established a multi-agency team, including the adviser, Connexions and social services.
"Training has been given to all housing options advisers and there is close liaison with other agencies dealing with young people to ensure joined-up working.
"Formal referrals to Kent County Council social services are undertaken as a matter of course and there is daily contact between Kent County Council and Dover District Council to progress these referrals.
"The operation of the protocol and its impact for young people locally is reviewed monthly by the housing options team and quarterly by Dover District Council and local agencies at our youth homelessness forum.
"The young person in question has been in allocated appropriate council housing since 2009, with tenancy support provided for the first two years.
"We continue to make improvements to our working practices.
"The local government ombudsman recommended actions that are already in place to prevent such a situation arising in future.
"The council is deeply sorry for any hardship suffered as a result of its actions before these improvements were made.
"The remedy proposed by the local government ombudsman will be actioned as soon as authority is obtained at the next meeting of the full council."