Post Office workers are staging a 24-hour strike on Thursday in a dispute over pay.
Members of the Communication Workers Union (CWU) who deliver cash and supplies to sub-post offices, process finances and work in administration are involved in the row.
The CWU said the action was in protest at a 3 per cent pay offer for the 2022-23 financial year, alongside a one-off lump sum payment of £500, and no pay increase for the 2021-22 financial year.
CWU assistant secretary Andy Furey said: “The blame for this disruption lies entirely with the senior Post Office leadership, who have repeatedly failed – and wilfully refused – to set out a sensible and fair pay agreement.
“Everyone knows that the only solution is a fair pay rise that properly rewards members for their extraordinary efforts in serving the public and delivering a profitable Post Office, while also taking account of the extreme cost of living.
“There most certainly is money available, but management do not want to give workers their fair share.”
A Post Office spokesperson said: “We have a range of contingency measures in place to minimise the impact of CWU strike action in our supply chain today.
“Our 11,500 branches are open as usual. We’re disappointed that the CWU have made the decision to strike but remain hopeful that we can reach a pay agreement soon.”
CWU members in Crown Post Offices went on strike on Monday, also over pay.
