Child sex abuse is rife and under-reported in remote WA Aboriginal communities, says the state's police commissioner, who is backing the State Government's push to close up to 150 of them.

The West Australian Government flagged the closure of the communities after the Commonwealth indicated it was withdrawing funding of critical services.

Commissioner Karl O'Callaghan said child sex abuse, substance abuse and family violence in some communities was extremely high, and their remote locations make it difficult to address the problem.

"Because they are so remote, the problem is so significant, we can't guarantee a good policing service to those places, certainly not at the level you'd expect for that type of problem," he said.

He said sex abuse was being under-reported by up to 90 per cent, and that girls as young as 11 had been prescribed birth control in some remote communities.

"They certainly have been given them, and this has been going on for some years," he said.

"It was a problem in Oombulgurri [a remote community shut down in 2011], ... and I only checked last week with my Kimberley management team to confirm that it is still a reasonably common practice."

He said the move to shut down some communities was practical.

"It's just impractical, and in fact it's impossible to provide the level of services that those communities need to deal with these intractable problems that they are facing," he said.

The Australian Institute of Family Studies (AIFS) data referenced by the commissioner refers to a 2000 study which concluded that up to "88 per cent of all sexual assaults in Aboriginal and Torres Strait Islander communities go unreported".

But it also stated that "less than 30 per cent of all sexual assaults on children are reported", indicating that the overall rate of unreported sexual assaults on children was 70 per cent.

The report also highlighted neglect, rather than sexual abuse, as the most common type of maltreatment experienced by Indigenous children accounting for 40 per cent of reported cases of harm, while sexual abuse accounted for 9 per cent of cases of harm.

Widespread abuse suggestion appalling: Aboriginal Legal Service

The Aboriginal Legal Service (ALS) said it was appalled at the suggestions of widespread abuse.

ALS chief executive Dennis Eggington said Mr O'Callaghan's comments were alarming.

"If the State Government and the police believe that this abuse has been occurring and continues to take place, then someone should be held accountable," he said.

"Because if this is the case, then the State Government has failed in its duty of care."

The WA Premier last month told Parliament that in 2013 there were 39 cases of gonorrhoea in Aboriginal children aged 10 to 14, but none in non-Indigenous children in the same age group over the same time period.

He has since conceded he did not know if the cases cited were from remote communities.

Premier Colin Barnett today said the Government and police had done much to address the problems of abuse, but it appeared beyond their resources.

"I do congratulate the Police Commissioner for having the courage to speak out and of course, policemen and women are on the ground, they can see exactly what is happening," Mr Barnett said.

"A lot has been done about it, but the task is probably impossible.

"If you just think of the logistics of 273 remote communities, many of them isolated, no sealed roads, cut off during flood times, and some of them very, very small, you are not going to be able to have police officers, child protection officers, health or education in all of those communities."

Police Minister Liza Harvey said she shared the commissioner's view on the difficulties of effectively policing small remote settlements, but could not yet say how many of those communities were beyond the reach or resources of police.

She said in communities of sufficient size, police and other agencies were able to work together effectively to deal with abuse.

"Obviously in those communities where we have our multifunction police facilities linked in with the courts and child protection officers and health workers, we're getting better outcomes," she said.

"But you need also to have a critical mass of people to warrant placing those facilities in those communities."