David Cameron yesterday insisted he has "every sympathy" with the parents of a severely disabled girl who say their daughter may have to go into care after he reneged on a pre-election pledge.
The Prime Minister said he would look into the case of Celyn Vincent "very closely", but denied the coalition's austerity measures were preventing the family getting more help.
The six-year-old has severe quadriplegic cerebral palsy and epilepsy and requires round-the-clock care. But her parents receive just six hours respite a week.
Ms Vincent criticised Mr Cameron and said the family was "crumbling".
Mr Cameron, whose son Ivan suffered from cerebral palsy and severe epilepsy and died in 2009 aged six, said: "I have every sympathy with the incredible difficulty that families have with bringing up disabled children, particularly when, as in the case of Riven's child, they are quadriplegic and have to have a huge amount of help around the clock, 24 hours a day.
"As Prime Minister, one of the things I am very keen to do is help families in this position and that is why, in a time of austerity and difficulty, we have put hundreds of millions of pounds more into respite care and into helping families who are looking after disabled children," he said.
"I don't believe there is a relationship between the cuts that are inevitably taking place nationally in some public services and this individual case."
Mr Cameron visited the family at their home in Bristol last April, after which they believed he would do more to help carers if he became Prime Minister.
But in a desperate plea posted on the parenting website Mumsnet, Ms Vincent announced she had asked social services to take Celyn into care.
"We only get six hours' respite a week. They have refused a link family. They have refused extra respite. I can't cope," Ms Vincent posted.
It provoked hundreds of messages of support.
In a statement yesterday, the mother criticised Mr Cameron for failing to improve the plight of carers.
"No one government is to blame. But I had hoped that, after David Cameron came to visit me earlier this year following our exchange on Mumsnet, he would have done more to protect families like ours.
"The money the Government has allocated for short breaks and respite care – 800m over four years – is not enough, and, worse still, it's not going to be ring-fenced. So there's nothing to stop cash-strapped local authorities from using the money elsewhere."
Ms Vincent described the demands of caring for her daughter as "relentless".
"She needs someone 24 hours a day. She must be tube-fed, is doubly incontinent, cannot walk, talk, sit up, or use her arms. She doesn't grow up. I sleep in a bed next to Celyn every night, beside a monitor that checks her breathing. I've barely had an unbroken night since she was born and I am exhausted."
Ms Vincent added that she was so tired through sleeplessness that she was unable to cook or give her three other children the attention they need.
She ended her statement by saying: "I have no wish to put my daughter in a home. We want to look after her. All I am asking for is a little more support."
A South Gloucestershire Council spokesman said: "The family receives a wide range of services and direct funding from the council and the NHS. This package of care is reviewed regularly and has increased according to need over the last six years. There have been no reductions in the care provided to Celyn and her family."