The mother of three children allegedly abused by their foster carer near Newcastle says her repeated complaints to welfare officials about their care were ignored.

The 47-year-old foster carer is charged with three counts of assault, as well as possessing a gun and drugs.

Police documents tendered in court this week allege the woman acted deliberately and frequently "whacked" the children with a stick, egg flip and belt, and put socks in their mouths while they were hit.

Police say all three had bruises, with doctors unable to count them all on one child.

The children's mother has told the ABC she had domestic violence issues when her children were taken.

She says she complained to welfare officials after several access visits with them.

"I tried to tell them months ago that my kids, on my visits, were telling me they were getting abused," she said.

But she doubts welfare officials took her complaints about the woman seriously.

"I'd spoken to DoCS previously about what my children were saying to me when I had visits with them," she said.

"They said it was investigated."

She says she wants some answers.

"I'd like to know what's going on with the Department of Community Services," she said

"They've just got to screen people properly.

"They assured me they were with a good family and that the children were progressing."

Welfare officials say they had no way of knowing the children could have been at risk when given to the foster carer.

The Department of Family and Community Services says none of its checks identified any issues of a criminal nature that would have given it any ability to predict that the children could have been exposed to harm.

The department says it is assisting police with their investigation.

It says the children are in a new placement, and it is working to ensure the children are supported.