Thousands of homeless children are growing up in cheaply converted shipping containers and cramped rooms in former office blocks, putting their health and wellbeing at serious risk, according to the children’s commissioner for England.

Anne Longfield said it was scandal that at least 210,000 young people in homeless families in England were put up by councils in temporary housing and bed and breakfasts or forced to “sofa-surf” with friends, often for long periods.

Such accommodation could be unsafe, disruptive and overcrowded, with no room for children to play or do homework. It was frequently in poor condition, far from family support networks and schools, and often in isolated locations dogged by crime or antisocial behaviour.

“Something has gone very wrong with our housing system when children are growing up in B&Bs, shipping containers and old office blocks,” said Longfield. “It is a scandal that a country as prosperous as ours is leaving tens of thousands of families in temporary accommodation for long periods of time, or to sofa-surf.”

Launching a report on family homelessness, she said the main causes were a lack of affordable housing and financial instability created by welfare changes, cuts to universal credit and a four-year freeze on housing benefit.

Shipping containers that have been converted to residential use for the homeless of Brighton. Photograph: Dominic Dibbs/Alamy Stock Photo

Corelle Tertullien, a mother of two, was previously housed in a hostel in Southall, west London, and moved into a container in Hanwell shortly before she was due to give birth in December.

“When I got the phone call, he said: ‘Oh, we have a flat for you’,” she told the PA Media news agency. “And then when I came here, I realised obviously this is not a flat. This is a shipping container. When they tell you, they make it out like it’s a flat or a house, but no, it’s a shipping container.”

Tertullien, who has two sons aged two and nine months, was forced to move out of her family home due to overcrowding and has to keep her belongings elsewhere because of a lack of space.

She said: “We’re all sleeping in one bed at the moment because I can’t fit the cot in here, there’s no space. There’s no bathtub. Originally I was washing him (the nine month-old) in the kitchen sink but now I wash him on the floor, getting a cup and washing him that way, because he’s too big to fit in the sink now.”

She said the lack of circulation in the metal storage containers means they were prone to overheating, which leads to condensation dripping from the ceiling.

Terminus House, a disused office building in Harlow, Essex, now being used for social housing. Photograph: Chris J Ratcliffe/Getty Images

“The fan is never off, it is constantly hot in here. The only way is to have your door open but I don’t want to have my door open because I don’t want people to look inside,” she said. “Most of the time they’re in their nappies because it’s just too hot.”

After almost nine months living in the container, the shop assistant is unsure when she will move into permanent accommodation. She said another resident had been living in a container for three years. “But to me, if it’s temporary accommodation, you shouldn’t be here for three years,” she added.

The report cites the case of Lucy, a homeless woman in her early 20s, and her two-year-old son, who were placed in a converted office block an hour away from their local area in London. The room had no basic furniture. Supposedly an emergency placement, they ended up staying for 11 months.

“They put me in a small room in an office block which had been converted into flats. It was in an industrial estate in the middle of nowhere. The cars and lorries would whizz round really fast. It was very noisy and it felt unsafe to walk to the shops,” Lucy said.

The NSPCC said such conditions were harmful to children. “These descriptions of pokey, dangerous conditions belong in a Dickensian novel, but instead they paint a picture of life in the 21st century for many families,” said the charity’s head of policy, Almudena Lara.

The report says one in 10 new homes created in England and Wales since 2016 are in former office blocks, rising to more than half in hotspots such as Harlow in Essex. A government rule-change in 2013 means such developments no longer have to seek planning permission. Councils have called for the rule to be revoked.

Many of the conversions fail to meet official size standards for a one-bedroom home, which is 37 sq metres. The report cites single-room flats of 18 sq metres converted from offices, and one of 13 sq metres – barely larger than a parking space.

Office-block conversions are often located on or near industrial estates, far from shops, schools and other amenities. Some children who live in them are reportedly stigmatised by peers as “office-block kids”.

Converted shipping containers are increasingly used by councils to provide temporary accommodation for homeless families. While some families prefer them to B&Bs because they have their own self-contained bathroom and kitchen, they are regarded as too hot in summer and too cold in winter.

The report says 124,000 homeless children were recorded as living in temporary accommodation in England at the end of 2018, an 80% increase since 2010. On top of this, it calculates there were 92,000 homeless young people in families who sofa-surfed with friends or relatives.

These estimates do not include a further group of children who have been placed in temporary housing by social services, for which there is no publicly available official data. Of those young people in temporary homes in 2017, more than half had been there for longer than six months, and one in 20 for more than a year.

The report says an estimated further 375,000 children live in households that have fallen behind on rent or mortgage payments, putting them at risk of becoming homeless.

The latest official statistics show 2,420 families were living in B&Bs in December 2018, a third of whom had been kept there for longer than six weeks, in breach of the law. These figures do not count at least 1,641 families in council-owned B&Bs, which are not included in official data.

The Local Government Association said a severe lack of social rented homes in which to house families meant councils had no choice but to place households into temporary accommodation including B&Bs.

A government spokesperson said: “No child should ever be without a roof over their head and we are working to ensure all families have a safe place to stay.”