The BBC report:
Members in administration and supply chain voted 76% in favour of strike action last Thursday. The CWU could not confirm the voter turnout.
The union said Crown post office staff had not had a pay rise since April 2011, while all other Post Office staff represented by the CWU had two pay rises in that time.
The union said a Freedom of Information request revealed that Post Office managers had shared a bonus of £15.4m in 2012-13.