A spokesman said the allegation had come from a member of the public.
He refused to reveal the age and gender of the worker accused. He also refused to reveal if it was an officer. He said no-one had been suspended or arrested.
"At the moment this is an allegation and we will not be releasing any information that may identify the person concerned," he said.
A West Mercia Police worker is being investigated after an allegation of rape, the force has said.