Many are multiple calls about the same families, and many require no further action. But even notifications of distinct individuals requiring further action have more than doubled, from 21,100 to 48,500.
Data for the past five years provided to Labour MP Jacinda Ardern shows that CYF staff numbers have also increased, but at a much slower rate, from 2741 fulltime-equivalents in June 2008 to 2938 in March this year.
After excluding specialist, contact centre and national office staff, the workload has increased from 16.6 notifications of distinct individuals requiring further action for every fulltime-equivalent local CYF worker in 2007-08 to 24.2 in the past year.
The northern (Auckland/Northland) region had a much higher notification workload than the agency's other three regions in 2008, and has gained 84 extra local staff since then.
The ministry's manager of ministerial and executive services, John Wilson, said CYF received an average of 145 requests for client files a week in the year to June, and this had increased recently to average 165 new requests a week.
"On average, a response will contain 400 pages of case file material. Case files will contain personal and sensitive information, and require careful attention when forming a response," he said.
"Given that, we estimate a response to a request for a current case file will be provided within two months.
"If it is necessary to extend the time frame beyond the 20 working days [under the terms of the Official Information Act] the requester will be advised of the reasons for this.
"If people require specific information within a file for a specific purpose, or if a request is determined to be urgent, we can work with requesters to speed up their request."