The number of Suffolk teenagers being housed in unregulated accommodation has more than quadrupled in the past decade – amid concerns about their vulnerability to criminals and paedophiles.
Official figures show 113 young people aged 16-18 in the county were in supported accommodation last year - up from 24 in 2009.
A BBC Newsnight report called Britain's Hidden Children's Homes, which broadcast on Monday night, found more than 5,000 children in England were living in unregulated accommodation - up 70% in the past decade.
Suffolk's figures were the fourth largest of all English local authorities.
Newsnight heard thousands of teenagers were being "dumped" in unregulated homes and "abandoned to organised crime gangs".
Jack Abbott, Labour's education spokesman at Suffolk County Council said he was "seriously concerned" that young people were being left vulnerable to exploitation.
"I sincerely hope that these young people in our care are not being forced into unregulated homes simply in order to cut costs," he added.
"A knowing failure to provide safe and secure accommodation would be a severe dereliction of duty from those in power.
"This is happening right here on our doorstep - the number of children being put at risk is frightening, so I hope SCC and the government will urgently review this alarming state of affairs."
SCC said it was confident about the properties, which were quality assured and regularly visited.
Councils place children in the homes to encourage independent living. They have support workers either living on the site or paying visits, but are not subject to the same checks and inspections as regular children's homes.
SCC spent more than £500,000 on the accommodation in April.
Almost 40% went to Sixteen Plus, a company which has previously been criticised for the quality of its housing in Norfolk.
Norfolk County Council temporarily stopped sending children to its homes while an investigation was carried out into photos which appeared in the Eastern Daily Press revealing the conditions some care leavers were living in.
A Sixteen Plus spokesman said more than 200 monitoring visits had been carried out at its premises since and "no issues had been found".
The spokesman said it was wrong to generalise about problems in unregulated accommodation as there were good and bad examples across all sectors.
"We work closely with the local authorities and any other agencies that may be involved to make sure that any risk is managed from the outset," he added.
"It's the multi-agency work that makes this effective."
Suffolk County Council said previously it was "fully satisfied" with the accommodation provided locally by Sixteen Plus.
Nationally, there are growing concerns about the effect of unregulated accommodation on vulnerable young people.
Jackie Sebire, National Police Chiefs' Council lead on serious violence, told Newsnight resources were being diverted to look for children reported missing from unregulated homes
Evidence gathered from police forces by the All Party Parliamentary Group for Missing Children and Adults highlighted further concerns.
Group chairman Ann Coffey MP said the survey revealed "a twilight world of homes that have become a magnet for paedophiles and drug gangs".
"Children are being dumped miles away from home in unregulated accommodation to fend for themselves and take their chances with what can be a very brutal and exploitative world," she added.
In response to Newsnight's investigation, Children and Families Minister Nadhim Zahawi said: "Children in care or those leaving care, including older children aged 16 and 17, deserve stability in their lives, including good quality accommodation.
"Semi-independent living can act as a stepping-stone for young people about to come out of care to help them prepare for the challenges of living as an independent adult.
"Local authorities are required to make sure that children in care and care leavers are given suitable accommodation to meet their needs, including that they are safe and secure which is why I recently wrote to all Directors of Children's Services to remind them of this obligation."
Council 'confident about accommodation provided'
SCC's cabinet member for children's services, Gordon Jones, said properties were quality assured and visited frequently by dedicated staff to manage placements and monitor living conditions.
"The council is confident about the accommodation provided," he added.
"We of course take any concern very seriously and do not consider accommodation to be a contributory factor to young people suffering abuse."
Mr Jones said the council had a very good relationship with its providers, including Sixteen Plus.
The council has a mixture of provision, including some that are registered with Ofsted and the Care Quality Commission, which are used for children with a high level of need, and others which are unregistered, where young people with good "self-care skills" are placed.
"This accounts for a very small percentage of young people in our care," Mr Jones added.
"There are alternative provisions for 16-17 year olds and we are one of the highest users of foster care in the Eastern Region. We also currently have 51 young people supported through the Staying Close support scheme and 43 young people in Staying Put arrangements post 18.
"There has been a noticeable increase in care leavers living in supported or semi-supported accommodation in Suffolk. This reflects Suffolk County Council's position in supporting the National Transfer Scheme, which is a central government initiative to encourage all local authorities to volunteer to support unaccompanied asylum-seeking children (UASC) to ensure a more even distribution of caring responsibilities across the country."
Partnership working
Suffolk Constabulary said it worked closely with partners and external organisations to identify and support young people at risk of falling into a life of crime.
"It is a complex issue and we need to do all we can to help those who have become involved in criminal activity through their vulnerabilities but still need support," a spokesman added.
"For example, those vulnerable adults and young people who are frequently used by drug dealers who take over the property of a vulnerable person."
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