Children wrecking the family home during a party may not be covered by household insurance, parents have been warned.
Nearly £17 million worth of damage a year results from parties getting out of hand, almost one in 10 of which - 54,000 a year - are held without permission.
In a third of cases the bill was limited to less than £100 - but 1% of parents report parties that caused up to £5,000 worth of damage during the past five years.
Around 38% led to some sort of damage, ranging from scuffed walls and broken personal items to structural damage.
Parents are now finding that in some cases their insurer will not cover the cost of the repairs, especially if the party was advertised on a social networking site.
Neil Laird, manager of Sainsbury's Home Insurance, said: "The rise of sites such as Facebook and Bebo has dramatically changed the way teenagers in particular invite 'friends' to their parties.
"It's not uncommon to have parties with many hundreds of people attending, and when such events get out of hand some insurers may suggest that the homeowner failed to take due care of the property and could refuse to pay up."
© The Press Association 2008