About 100 workers at the Australian Red Cross Blood Service in Melbourne are set to walk off the job on Wednesday.   

Health Services Union (HSU East) deputy general secretary Marco Bolano said workers were unhappy with enterprise bargaining negotiations and would stop work for four hours on Wednesday afternoon.

Mr Bolano said management wished to cut long service and sick leave entitlements and to remove the ability for Fair Work Australia to arbitrate on industrial matters.   

"Our members are walking off the job today for four hours because we've been attempting to resolve an enterprise bargaining agreement for months and the Red Cross Blood Bank haven't backed down," Mr Bolano told AAP.   

However he said people would still be able to donate blood through the stop-work action.

"No' we're not going to do anything that's going to impact on that sort of thing, we won't touch the essential services," Mr Bolano said.

A Red Cross Blood Service spokesman said the group was "in the process of negotiating a new agreement with staff, and will continue to engage in good faith discussions with staff to achieve a resolution".