More than 80,000 children in the UK will spend this Christmas homeless, with the number of families due to be in emergency housing over the period at a 10year-high.
The homelessness charity Shelter has launched an emergency appeal following an investigation into the "shocking conditions that many homeless children will be living in this Christmas".
Campbell Robb, chief executive of Shelter, said children were being forced to eat on the floor, share beds with parents as well as being threatened with violence.
"This shouldn't be happening in twenty-first century Britain," he said.
The charity's report, which focused on those living in local B&Bs, concluded: "The majority of the families were living together in one room, while in over half of the cases investigated, children were sharing beds with their parents or siblings.
"Two thirds of families said that their children had no table to eat meals on, and often had to eat on the floor or on the bed"
One mother told Shelter she was "scared" for her son after being evicted by their landlord and relocated to temporary accommodation in Hounslow, west London.
Joan, a GP receptionist from Hillingdon, said of her seven-year-old boy: "It's so hard to give him a balanced diet as it's impossible to make proper meals here, let alone a Christmas dinner.
"He's getting really pale and is so tired all the time. He gets so scared but it's difficult when I'm scared myself. This is no place for a child to live. We're desperately hoping we won't be here for Christmas."
Her son added: "Sometimes it's scary. There's no room to play here and I miss having my friends over."
The charity's warning is based on figures released by the Department for Communities and Local Government that show 82,528 children were in temporary accommodation in March this year.
Shelter spent time with 25 families living temporarily in B&Bs, up to half of whom complained of having to share a bathroom and kitchen with strangers.
A further 22 of the families said that it was difficult to find a safe place for their children to play, while those with children of school age said there was nowhere for them to do homework.
Campbell Robb, chief executive of Shelter, said: "Our shocking findings have uncovered the shameful conditions homeless children will be living in this Christmas.
"Parents and children sharing beds, children forced to eat on the floor and being threatened with violence in the place they live: this shouldn't be happening in twenty-first century Britain.
"No child should be homeless, let alone 80,000. But tragically, with more people struggling to make ends meet and homelessness on the rise, we're bracing ourselves for an increase in demand from families who desperately need our help."
Mike Jones, chairman of the Local Government Association's environment and housing board, said: "Local authorities work hard to find appropriate accommodation for people who have lost their homes, and the needs of families with children will always be a priority.
"No council ever wants to place a family in bed and breakfast accommodation but, with growing demand for help and a chronic shortage of affordable housing, this is sometimes the only option available to keep a family together with a roof over their heads.
"Shelter's report highlights exactly why house-building needs to be a national priority. Government's efforts to increase house-building must ensure that new affordable housing is built as part of developments.
"Councils could make a significant contribution if the Treasury lifted the housing borrowing cap which would enable local authorities to build up to 60,000 additional new homes over the next five years.
"Government's welfare reforms will mean more people turning to their council for housing support.
"With more than four million people on council housing waiting lists and not enough homes to go around, action needs to be taken now to get more new affordable homes built."
Housing Minister Kris Hopkins said: "We've given councils nearly £1 billion to tackle homelessness, and to support people affected by the welfare reforms so I am very clear that they should be fully able to meet their legal responsibility to house families in suitable accommodation.
"Families should only be placed in bed and breakfast accommodation in an emergency, and even then for no more than six weeks.
"The funding we've given, and our change in the law to enable families to be placed in suitable, affordable private rented homes, means there is no excuse for councils to breach this."