Internal documents have revealed a state government plan to cut the Family and Community Services budget by $70 million and reduce staff numbers by 30 per cent.

The document titled Changing the Way We Work on the department's letterhead says that starting in July this year, the department must make an annual saving of $70 million.

Labor claims vulnerable children will be put at risk by cuts.

"The majority of these savings will come from staff reductions in the central parts of FACS where we will need to be 30 per cent smaller," the document says.

"Savings are allocated across the NSW Government and FACS is no exception."