It's the little things that can tip you over the edge, says Asher Nardone, mother of two boys, one of whom is disabled. “On Sunday, Callum was sick on his bed, so I showered him and washed his sheets. Then he pooed in his bed, so I washed his clothes and sheets again. Then he spilt milk over his bed, so the sheets had to be changed again, and after that he spilt baby oil over the bed. By lunchtime, I'd had to do four washes.

“Every day, I'm living in a fragile state, running on exhaustion, asking if he's OK, if his brother's OK and can I work today. I never get a break. I have to look after him with flu, a bad back or sore arm. It's not his fault, but it's the grind.”

Asher, 38, lives alone in Poole, Dorset, with her sons, Callum, a profoundly disabled 12-year-old, and Guarin, 10. Theirs is one of more than 700,000 families in the UK living with a child with a serious disability. Many of them face daily battles with schools and social services to be given help.

On Tuesday, Joanne Hill was sentenced to a minimum of 15 years in jail for drowning her four-year-old daughter, Naomi, in the bath. Hill was embarrassed by her. Naomi suffered from cerebral palsy, which meant that she had to wear calipers to walk, and had poor hearing. After killing Naomi, Hill bought a bottle of wine and drove around drinking for eight hours before taking her daughter to hospital.

Hill, who had previously suffered puerperal depression, the most severe form of postnatal depression, denied murder on the grounds that she was suffering from a severe mental illness. But the jury took just 90 minutes to convict her of murder. Her husband later described her as evil.

But Hill's is not an isolated case. While most parents love their disabled children unconditionally, they are also worn out by endless battles for the services they are entitled to.

The controversial debate of terminations in the Human Fertilisation and Embryology Bill returns to Parliament in the coming weeks. Some parents say that if they had known how difficult life was to be with disabled children they might have reconsidered their choice.

While it is unclear how much support Hill was offered by social services, her cries for help were clearly not heard. Yesterday, mothers of disabled children were slower to condemn her and pointed out that asking for your child to be adopted does not mean that you are an uncaring mother, but that you know someone could do your job better. After six years of struggling to cope with Callum on her own and being forced to take her council to court for everything from the house they live in to an extra nappy, Asher said she could sympathise with Hill: “Desperate people do desperate things. I'm strong and determined, but I've had to fight for nappies, housing, transport for Callum and to set up a business. Some people don't have those reserves and it just sends them over the edge.”

Twelve years ago, life was very different. Asher was living in Buckle, a fishing village on the Moray Firth, with her husband. She caught a virus while pregnant, but no abnormalities were discovered until she was 20 weeks pregnant. She was offered a termination, but was constantly told that her son's problems were 'borderline', so she chose not to. But Callum was born with cerebral palsy, two club feet, kidney problems, partially blind, unable to use his left arm, and badly epileptic. By the time Callum was five, and Guarin 3½, the marriage had broken down.

With the mental age of 18 months, Callum will “bomb everywhere like a big two year old” on all fours. He has a great sense of humour, but can speak just a few words and occasionally a full sentence. He can open bottles and pick up sweets with his right hand, but his left is floppy all the time,” says Asher. “He's like a one-year-old, except a one-year-old starts learning not to, and Callum never does.”

After the split from her husband, Asher decided to move closer to her family and a job in Poole. But having had excellent care and help in Scotland, where someone had come in to do the washing, give her respite care at weekends and pick up Callum for days out, in Poole her world “fell apart”.

“There was nothing. Not an hour's care. The whole safety net collapsed and they just said it was down to funding and that budgets were being cut,” said Asher. “I'd had to leave all his equipment in Scotland and they couldn't replace it.”

Having just started her new job, she soon lost it and could not find another. They were made homeless, and as she could no longer afford the rent, they ended up in social housing. But after six years, Asher is still having to fight: for a downstairs bathroom in her council house; for appropriate transport for Callum; and to set up a jewellery business.

In December, Asher suffered a “crisis”. She went to social services, but the only option offered was residential care for Callum in Exeter, two hours away.

Julie Evett, 30, who lives with three daughters in Gainsborough, Lincolnshire, also took a long time to admit that she was unable to cope before calling social services. While Alanna, 11, and Nicole, 7, are both healthy girls, her youngest, Rose, 2, is very disabled.

Registered blind, Rose has suspected cerebral palsy, epilepsy and hypotonia, which means that her body is as floppy as a newborn baby's. She cannot turn on to her side on her own or even hold a bottle. She goes to nursery, but increasingly needs one-to-one care. While Rose qualifies for the highest rate of disability care allowance, she is not entitled to the mobility element of the Disability Living Allowance. So the family is often stuck at home.

Like Asher, Julie has called for help from social services four times and has heard nothing. She is asking for a mere two hours' help a day after school. “The only time I was referred was when I slapped Nicole on the leg during a tantrum,” she says. “I wasn't proud of myself but Rose was in hospital and I had to go down to the police station and wait three weeks to hear whether I was going to be charged.”

The case was not taken any farther. But during that time, Julie was “worried sick” that if she were charged for assault, her burgeoning career as a teacher would be over. Having separated from her partner within weeks of Rose's diagnosis at three months old, Julie has no other income except that as a “cover supervisor” at school, earning £11,000. According to Julie, such tragedies as Naomi Hill's murder may be avoided if social services took parents' cries for help, such as putting up their child for adoption, seriously.

At Contact a Family, the only charity in Britain to help the families of disabled children, Srabani Sen, the chief executive, says Asher and Julie's cases are not uncommon. And while the Government is trying to co-ordinate services with its Aiming High for Disabled Children agenda, it will take time to bring them together across the country. “Historically it's been a very low national priority. The Government has made a good start, but it could take up to a decade to transform the system.”

Julie cannot wait for social services to catch up. Instead, she has taken her plight to the internet. On Facebook she discusses her pain with other parents in similar positions. She says it has made her realise that there are “many parents at breaking point”.

In the last parliamentary session, MPs tried to reduce the upper limit for having terminations from 24 to 20 weeks in the Human Fertilisation and Embryology Bill. Parents of disabled children will be following the outcome closely.

Asher says she would have accepted an early abortion if she had been told that her child had Down's Syndrome or spina bifida because it would have been “clear-cut”. Julie believes that she would have gone ahead with a full-term pregnancy at the time, but “knowing how difficult it is now and put in the same position again, my answer would probably be different”.

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