The negotiations officer for the Prospect union says government plans to resource swine flu information and medicine distribution points are 'wasteful and ill thought out'.
Angela Moffatt also believes it's a lost opportunity to offer jobs to the unemployed.
The Chief Secretary has sent a circular asking for volunteers to staff an information phone line and medication collection points.
The work would be undertaken during normal office hours with overtime being paid after office hours and at weekends.
Ms Moffatt says there has been no consultation with the union over the plans, despite them pushing for several years for effective arrangements to be made for such a scenario.
She also says it highlights the contradictory approach of the government to public sector pay and resourcing.
A Government spokesman has said the idea of using existing public sector staff as volunteers is that they're more likely to be used to dealing with confidential information, dealing with the public and will need less preparation for the role.