Post Office workers have voted by almost 9-1 to take strike action in a dispute over pay.
The Communication Workers Union (CWU) balloted around 4,000 of its members who work in the Crown post offices - the larger sites usually based in high streets.
There was an 88% majority in favour, in a turnout of 75%.
Dave Ward, CWU deputy general secretary, said: "Our Post Office members have spoken loud and clear in this ballot. They are fed up with being treated like second-class workers by the Post Office and they want their concerns to be listened to.
"There hasn't been so much as the pretence of negotiations from Post Office Ltd and that must change if strike action is to be avoided. We are now asking the company to come to the table to discuss pay and job security for these workers and avoid the need for strike action."
Andy Furey, CWU official for Post Office members, added: "The Crown network brings significant revenues into the business and is crucial to the effective delivery of many products and services.
"The company has given pay rises to other employees and now it's time they played fair and awarded a pay rise to Crown office staff. Job security and the future of the network are the elephant in the room here and we want to see the Post Office acting as a responsible and fair employer, not treating parts of the workforce differently and gambling with services which communities rely on."