The study asked children about their roles

The survey by the Princess Royal Trust for Carers found that 14% of seven to 19-year-olds looked after someone with illness, disability or health problems.

This would correspond to 115,000 youngsters acting as carers, more than five times higher than the figure for under-19s in the 2001 census.

The trust said the study should act as a "wake-up call" for local councils.

Louise McDonald, a carer services co-ordinator for the trust, said it was thought to be the first time a national survey was conducted where young people themselves were asked about their caring situation.

We believe that only a tiny percentage of young carers are getting the help they need Louise McDonald The Princess Royal Trust for Carers

Ms McDonald said the census was filled in by parents of young people, who may not necessarily admit that their child is looking after them or a brother or sister.

She added: "We believe that only a tiny percentage of young carers are getting the help they need.

"More detailed research needs to be done, but these figures should be a wake-up call for those local authorities who ignore the needs of young people who look after someone.

"Agencies that support adults have not often considered to what extent the support package they have put in place relies on the hidden caring of a child.

"If they asked the adults whom they support a few simple questions, that could change."

The trust said tasks ranged from personal care for a physically disabled adult, making sure a brother or sister with a learning disability played safely, or staying in to be there for a parent who misuses substances or has a mental illness.

The survey questioned 1,320 young people across the UK and found the highest proportion of youngsters acting as carers in the East Midlands, with 19%, followed by the north of England, at 15% and 14% in Scotland.