Jim Reeves, from the Communication Workers' Union, says the argument to close 70 Crown Post Offices is flawed because the business is profitable.
He spoke to ITV News Central outside the Kings Heath branch in Birmingham as staff went of strike this morning.
More top news
A mother who told her son she was going to the supermarket - before flying to Australia - has been given a six-month suspended sentence.
As temperatures fall this weekend the amount of sunshine we will see is on the rise. After a mild November, December is off to a cool start.
Breaks in the cloud overnight will allow mist and fog patches to develop. Sunny spells developing tomorrow.