The Department of Community Serviceshas admitted it failed to fill child protection staff vacancies across the state, including 70 positions in central Sydney, to meet budget restrictions.

Internal government correspondence released in an upper house call for papers shows Family and Community Services Minister Pru Goward's office asked her department why ''we are now still needing to reduce staff numbers to live within budget''.

The documents show her office was asking questions as early as February this year about why the number of caseworkers in Wollongong appeared to have fallen by 25 per cent.

In Parliament this week, Ms Goward rejected a Fairfax Media report showing the number of caseworkers in Wollongong fell by 25 per cent - from 44 in June 2011 to 39 in June last year and to 33 in December.

She said budgeted positions had been constant during 2011 and 2012 at 37.7 full-time equivalent positions and the Wollongong office had been overstaffed.