Concerns outsourcing payroll jobs could expose public servants' private data have been downplayed by the NSW government.
The NSW government has hit back at claims the private data of thousands of workers could be exposed as jobs are sent offshore.
The Public Service Association on Wednesday said its members were worried their data was at risk due to the state government's plan to move some payroll and finance jobs overseas.
Payroll and finance functions for Revenue NSW will be outsourced in October to GovConnect, a firm run by American tech giant Unisys and Indian tech behemoth Infosys.
GovConnect already provides shared services for several NSW departments.
"The department has a legal obligation to ensure the privacy of its staff details - the PSA is not convinced offshoring the vital payroll system meets those obligations," PSA general secretary Stewart Little said in a statement.
But the finance, service and innovation department insists it has secure systems in place to protect data and strict guidelines that GovConnect must adhere to when accessing information on public servants.
"This information does not include details relating to workers' compensation or medical information," a spokesman told AAP in a statement.
"The majority of DFSI employee information is processed in NSW, not offshore, and is safely stored on the state-owned HR/payroll system located in NSW."
NSW started using GovConnect from late 2015.
Unisys told AAP on Wednesday that 90 per cent of its 128 staff supporting GovConnect are based in NSW and "Unisys does not provide the payroll system."