A NSW deputy state coroner has described the death of a morbidly obese 13-year-old girl, who died in abject squalor after her parents failed to get her medical help, as "very sad" and "completely preventable".

An inquest into the Illawarra teen's 2014 death heard that her parents had driven to their vermin-infested home after playing two-up at a nearby pub to find their daughter, who weighed 112kg, screaming for her asthma inhaler.

Deputy State Coroner Geraldine Beattie found the child’s weight and the home’s condition, which was overrun with mice and rancid with mould, probably contributed to the girl's chronic asthma, which she had suffered since 2005.

Police said they were forced to don breathing masks upon entering the home, so rank was the smell.

The child was so panicked at having lost her puffer that her mother, who cannot drive due to mental problems, asked the father to take her to hospital.

However the father refused, saying he was too drunk to get behind the wheel.

He "simply went back to bed in the garage and removed his hearing aids", the coroner said.

As the Illawarra Mercury reports, the inquest found the girl's weight, the condition of the house, and exposure to her father's cigarette smoke, as well as the family's failure to properly administer her asthma treatments, were all factors in her death.

The girl's mother could be heard screaming hysterically during the triple-0 call the family made after the father discovered her body about 6.50am on April 26.

Though the girl was rushed to Wollongong Hospital, events to resuscitate her failed and she was declared dead shortly after 9am.

"This has been a very sad case," Deputy Coroner Beattie said.

"Deaths from asthma are relatively uncommon and (the girl’s) death was so very clearly preventable. (She) was so young when she died and her experience of childhood fell below what we would hope was acceptable."

Although the coroner noted the "family struggling to cope with day-to-day life," the inquest also found that the response from Family and Community Services – to which the family had been reported 19 times – was insufficient.

The girl's case had been closed by FaCS in June 2015 "due to competing priorities", which Coroner Beattie described as typical of a department's resources "being stretched to the limit".

"It is clear from this table (of reports to FaCS) that there were too many missed opportunities for FaCS to investigate and take supportive and/or protective action," Coroner Beattie said.