A hospice charity that works with children affected by life- limiting illnesses has warned families it will have to withdraw its services from young people who are surviving much longer than ever expected.

The Children's Hospice Association Scotland (CHAS) provides end-of-life care for children who are terminally ill, and respite breaks for children with life-limiting conditions.

While it does not usually start working with young people of 16 or above, it has never had an age limit on how long existing users can carry on going to its hospices – Rachel House in Kinross and Robin House in Balloch.

However, children suffering from conditions such as muscular dystrophy, who were not expected to live past their teens when they were diagnosed, are now often living into their 20s and even 30s.

CHAS chief executive Maria McGill wrote to the families of more than 100 young people this week to tell them the charity can no longer cater for young people aged 21 or above, and services will be gradually withdrawn from this group over the next three years.

She said: "We see an increasing number of young people who perhaps now live into adult life when previously they may not have expected to. We have been thinking seriously about what this means for CHAS."

Ms McGill told The Herald that services provided at the two centres were less satisfactory or appropriate for young adults, and it was not necessarily suitable for them to be coming to stay for respite breaks alongside much younger children or even babies who might have a much shorter life expectancy.

CHAS has pledged to work with families to ensure there are alternatives in place, but the major policy change has provoked anger among some parents who say the alternatives simply are not there and the charity is reneging on pledges made to them.

Eunice Watson, whose son Robert began attending Rachel House 15 years ago, said the families and young people affected had not been consulted about the decision. She said: "I don't know what we are going to do. When the charity was set up, the pledge to parents was that it would be there for them from the point of diagnosis to the point of death, and beyond. Now the parents are being pushed aside by the professionals."

The five stays Robert, now 27, has every year at the hospice are crucial for the family, as he needs year-round 24/7 care, she said, adding: "It would be different if there was something out there for them, but there is not."

Ms McGill said she understood the concerns of parents, and said there was a lack of suitable services for people aged 25-45, with adult hospice services set up largely to cater for much older adults suffering from cancer and other terminal illnesses. However, she said CHAS was talking to other hospices and care providers to see if some could provide facilities for young adults. She said she had received an enthusiastic response.

The charity will also work with politicians and civil servants to highlight the gaps in services, she said.

"We are not the society we claim to be if we don't address this," she said. "I am telling families that if, after three years, we haven't met their needs somewhere else, I will consider we have failed."