The number of abused children in state care has gone uncounted for 18 months, after years of reporting them.
The Ministry of Social Development has included this number in its annual report since 2010/11. Almost 170 children were found to be abused in state care from 2010 to 2015. But the number was not included in the last report for 2015/16.
Green Party social development spokeswoman Jan Logie said this was "blase and shows an unwillingness to be accountable". She said she believed measuring how many young people are abused by Child Youth and Family caregivers was a key step to stopping the abuse.
"There has been a 25 per cent increase in the young people abused by CYF-approved caregivers since the government started counting so we haven't been on the path to making kids safer.
"It should matter to the Minister how many children and young people are being abused during this time of transition."
The number steadily increased from 30 children in 2010/2011 to 40 children reported as abused in MSD's 2014/2015 report.
The Minister of Social Development Anne Tolley told Logie that the number was excluded as the reporting methodology is changing dramatically. She said that all types of abuse will be considered, not just serious abuse.
Ministry for Vulnerable Children, Oranga Tamariki spokesman Greg Versalko said a 2014 review found that the previous methodology had a narrow focus.
"The number of children abused while in Child, Youth and Family care in the 2015/16 financial year is, therefore, not available. A new methodology is being applied and data is currently being gathered and analysed.
"The safety and wellbeing of the children and young people in our care is paramount and as a new Ministry we are on a journey of transformational change to deliver positive long-term outcomes for vulnerable children and young people."
Logie suggested that the government could continue to report on serious abuse while it adds a new category for other abuse under when they developed the new methodology.
The MSD 2010/2011 annual report stated that from that year it would report nationally on children in care who have been abused. The report said that this was an "important step to ensure the safety and quality of our care is monitored on a regular and ongoing basis".
Tolley and Prime Minister Bill English have so far refused an independent inquiry into the historical abuse of children in state care. Logie said this was another example of the government shirking responsibility and failing to make children safer.