Post Office staff who work in the company’s supply chain have voted in favour of strike action over pay.
The workers – who deliver and collect cash from post office branches – backed strike action by 76%, the Communication Workers Union (CWU) said.
The CWU said that a pre-Christmas strike was looking "inevitable" because the company was "refusing to negotiate".
The Post Office said its offer was "fair and affordable".
It added that any strike action would not include employees working in the Post Office’s 11,500 UK branches.