Postal workers have voted to strike over job cuts, branch closures and pensions, the Communication Workers Union (CWU) has announced.
The union said the Post Office was "on the path to extinction" as the ballot saw an overwhelming majority of 83.2% vote in favour of industrial action.
The union said workers face 2,000 job cuts and the closure of a pension scheme in a "strategy of slash and burn" by the board of the company.
CWU general secretary, Dave Ward said: "The Post Office is at crisis point and the government has to step in."
Some 3,500 union members from Crown offices, supply chain depots and administration sites were balloted, the union said ahead of the vote.
It was said to be the first time workers from different parts of the business were balloted together.
The industrial action comes amid concerns that public funding for the Post Office has been withdrawn and revenues have stalled causing staff and customers to pay the cost, the union said.