Cadbury's operations in Ireland face disruption from next Thursday as SIPTU and Unite have served strike notice on the company.
Unite Regional Coordinating Organiser Richie Browne said that workers were furious that the company - now known as Mondelez - was unilaterally implementing a Labour Court recommendation which had been rejected by union members.
The changes include the outsourcing of the work of 17 employees based in the stores operation, which is viewed as a core function.
The strike will commence next Thursday at 7am and will involve a full withdrawal of labour until the matter is resolved.
Mr Browne said SIPTU and Unite represent around 350 of the 900 employees at the plant at Coolock in Dublin.