NSW Family and Community Services Minister Pru Goward has been accused of spinning "a web of deceit" about caseworker numbers.
The NSW opposition on Wednesday released a series of internal emails showing a drop in numbers at an office in Wollongong.
They show that while the office had 43.9 full-time equivalent staff in June 2011, this had decreased to 32.7 by December last year.
The emails indicate positions were set to be cut to 29 full-time equivalent staff from January of this year.
The revelations come more than a year after Wollongong caseworkers walked off the job in August, sparked by the death of two-year-old Zoran Ivanovski from a serious head injury.
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The boy had been reported to the department in the weeks leading up to his death.
The Public Services Association of NSW (PSA) said then that "protracted understaffing and ongoing job cuts" meant caseworkers simply didn't have the resources needed to follow up at-risk children.
Ms Goward maintained on Wednesday that at the time of the two-year-old's death the Wollongong office was overstaffed.
"They were slightly over their budgeted allocation of 37.7 positions," she told Fairfax Radio.
But Opposition Leader John Robertson accused her of playing with the numbers.
"She is looking to complicate a situation because she has spun such a web of deceit," he told reporters.
"This minister can try and dress it up, she can mince her words.
"The fact is there has been a reduction from 44 to 33 staff in an 18-month period."
It was time for Ms Goward to resign, he said.
"If she doesn't, then (Premier) Barry O'Farrell needs to explain why it is that he thinks it is appropriate for Pru Goward to sit on his frontbench."
Ms Goward said it was up to the department to decide where positions are filled.
