The Communication Workers Union (CWU) claims that plans to close or franchise 70 of the UK’s biggest post offices - known as the Crown network - will affect hundreds of jobs.
Dave Ward, the CWU's deputy general secretary, said, "Our Post Office members are standing up against destructive plans which would slash 20% of the Crown network and are simply asking for fair treatment and job security.
"The Post Office's plans are short-sighted and would rob the network of the most productive offices while simultaneously putting hundreds of jobs at risk and potentially damaging local economies.
“We'd like to see a better vision for a successful network which maintains services in the heart of communities alongside quality jobs.
"We're confident this could be achieved if Post Office management would agree to negotiations".
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