Hundreds of managers are to join a strike by Post Office workers in a long-running row over pay, jobs and branch closures.
Unite, which represents 900 managers, predicted that hundreds of Crown offices will close on Monday as a result of the co-ordinated walkout.
Members of the Communication Workers Union (CWU) will be taking their 13th day of industrial action this year in protest at plans to franchise or close over 70 of the Crown offices, the larger branches usually sited on high streets.
Unite said managers will also strike, for 24 hours, over a 16-month "failure" to reach a fair pay settlement, adding that its members have not received a pay rise since June 2011.
Unite official Brian Scott said: "The industrial action we are taking with the CWU is set to close almost 300 post offices in the Crown network on Monday.
"While we understand that this will cause inconvenience to the public, the ball is in the management's court - as it has been for the last 16 months - to reach a fair and equitable settlement.
"Unite is ready to have talks at any time with the Post Office to resolve this matter, but the management has taken a very hardline stance against our members who have seen their living standards seriously eroded."
PA
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