More than 80,000 children in the UK face spending Christmas living in "shocking conditions" in temporary housing, according to charity Shelter.
It says the number of families living in emergency accommodation - often in a single room - is the highest it has been for 10 years.
This means many children don't have proper homes to live in.
The Local Government Association said there's a shortage of housing that families can afford, so B&Bs are the only option in some cases.
But Housing Minister Kris Hopkins said councils have already received nearly £1bn to tackle homelessness.
Shelter's warning is based on research by the Department for Communities and Local Government that show 82,528 children were in temporary accommodation in March this year.
Struggling to do homework
Looking at London, at the end of June, 62,394 children were living in temporary accommodation, compared with 57,269 in the same month in 2012.
The charity spent time with 25 families living in B&Bs and up to half complained of having to share a bathroom and kitchen with strangers.
Twenty-two families said it was difficult to find a safe place for their children to play, while others struggled to find somewhere to do homework.
Joan, a GP receptionist from Hillingdon living in temporary accommodation in Hounslow, west London, with her seven-year-old son, said: "It's so hard to give him a balanced diet as it's impossible to make proper meals here, let alone a Christmas dinner.
Her son added: "Sometimes it's scary. There's no room to play here and I miss having my friends over."
Mike Jones, chairman of the Local Government Association's environment and housing board, said: "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."
But the housing minster said: "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."