WORCESTER Post Office is set to move into the city's WH Smith store as part of a national move.
Worcester's Foregate Street office is one of 70 nationwide set to close with services transferred to the High Street giant.
But the Royal Mail is facing the threat of strike action after the announcement.
The Post Office said following a trial in six areas, a further 70 so-called Crown Post Offices are expected to move to WH Smith by the end of summer next year.
Managing director Alan Cook said the combination of the Post Office and WH Smith made "perfect sense" for customers because there were natural links between the products both organisations sold.
But the Communication Workers Union (CWU) attacked the announcement, warning that more than 3,000 experienced staff faced losing their jobs.
The Post Office dismissed the figure and said around 1,300 workers would be affected.
The union said all its members in the Post Office will now be consulted for national strike action.
General secretary Billy Hayes said: "This is moving from trusted public servants to a company which regards postal services as a sideshow."
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