Government employees who continued working during Monday's national strike claim they were told to pretend to be answering machines to cope with an overload of calls from the public.
Staff at the Department for Work and Pensions in Carlisle said they were given a brief script to read out, in the style of a telephone answering machine, before hanging up.
The instruction by managers was leaked on Facebook after chit-chat between strikers from the Public and Commercial Services Union and their colleagues who had stayed at work. One said: "To begin with, we all found it hard to keep a straight face, and occasionally, I slipped up and I ended up giving my name to the person who was calling."
The staff said their fake-robot message was issued for peak lunchtime, between noon and 2pm. The script read: "Due to the high volume of enquiries we are currently experiencing we are unable to take your call. Please call back later."
Last night, a spokesman for the DWP said claims that staff were forced to pretend to be answering machines were "absolute rubbish".