Annual workforce statistics produced by the Department for Education show that the average caseload for social workers in England, as of 30 September 2017, has risen to 17.8, up from 16.1 the year before - an increase of 1.7 cases, although the DfE has said that the data should be "viewed with caution".
Average caseloads were found to vary between local authorities, between 10.2 for Kingston upon Thames and Richmond upon Thames, up to 26.4 for Staffordshire.
Information on social worker caseloads was first collected on a mandatory basis last year - but the DfE has said that differences in the way this year's data was measured means it is not comparable to previous years.
"The data items have been collected at an individual social worker level for the first time this year and allow us to calculate a specific caseload measure but they are not comparable to data from previous years," a report featuring the statistics states.
"Local authorities have reported difficulties with linking the number of cases and the social worker holding those cases so care should be taken interpreting the figures."
Higher caseloads have previously been linked with an increased likelihood of children being re-referred to child protection services.
The report also reveals that there has been a three per cent rise in the number of full-time equivalent children and family social workers up to 28,500 as of 30 September 2017 up from 27,700 the previous year.
The number of agency workers fell very slightly from 5,340 to 5,330 over the same period.
Meanwhile, the turnover rate - defined as number of leavers divided by the number of workers in place at 30 September 2016 - was 15.1 per cent.