Philip Telfer said his son Christoher gives his life 'purpose'
A couple invited to 10 Downing Street to talk about caring for their autistic son said they were unable to go because they could not find respite care.
Philip Telfer said the situation was typical of the struggle carers face.
He and his wife Julie look after 20-year-old son Christopher, full time at their home in Abersychan, near Pontypool.
The couple were among people from 10 charities invited to a reception at Number 10.
The couple, who are members of Carers UK, say the stress of caring for their son, who has profound learning difficulties, has left them with health problems, including anxiety, stress and depression.
Mr Telfer, 47, needs an operation this month to have a malignant growth removed from his face. It is his second brush with skin cancer and his third with cancer.
He first learnt he had cancer in 1993, the year his middle son Craig, eight, was knocked down and killed when he was on his skateboard.
He said the tragedy made the couple determined to have Christopher at home as long as they could.
"With Christopher, if he didn't have the difficulties he does, I don't think we would carry on. He gives us a purpose to life," he said.
They live in a three-bedroom social housing property purpose-built around Christopher's needs.
The couple campaign for more resources for carers, claiming they have been told residential care for their son would cost £500,000 per year. Mr Telfer would like to see a database of carers in Wales.
Mr Telfer said: "They make you feel awful for being a carer and like you are sponging off the government. I had to give up work because Julie can't manage Christopher.
"If Christopher is at what I call an eye-level of aggression, it can take three of us to look after him. He is doubly incontinent and he needs his pad changed."
He said he was disappointed they had not been able to take up the invitation to number 10.
A spokesman for the Gwent NHS Trust said: "We can give Mr and Mrs Telfer the total re-assurance they are seeking regarding the care package they will receive, which is specifically designed to address the issues they are concerned about.
"Other packages will be available to support families facing similar care issues, each designed for the individual patients and their specific needs."