Aberdeen City Council spent nearly £8 million on hiring agency staff last year.
A report to the audit committee showed £7.9m was spent on temporary staff for the year 2015/16.
Fears were raised that the workers are not being trained properly to EU standards.
The figure compares to £6.6m in 2014/15 and £7.3m in 2013/14.
The report stated: “Testing identified significant levels of off-contract spend, resulting in a failure to comply with EU procurement regulations, and issues with regard to the recording of induction checks and compliance with European working time directive requirements.”