Parents are spending an average of £465 a year looking after grown-up children who have returned to the family home.
Research by Sheilas' Wheels found the boomerang generation – sons and daughters who have flown the nest and then moved back in – stay for between three weeks and 12 months.
Indeed, 26 per cent of these youngsters have moved back home long-term because they cannot get a mortgage or afford to rent.
Jacky Brown of Sheilas' Wheels home insurance said: "What is really worrying is that it is not just the financial implication of housing [returning children] that is a concern, but also the pressure it puts on relationships."
Aside from putting an economic strain on households, parents said the biggest annoyance of having kids back at home is that they leave a mess lying around (38 per cent), followed by the fact they do not offer to contribute to bills (29 per cent) and never say thank you (28 per cent).