Although positive that the impact will be minimal, the Post Office says it is “extremely disappointed” that the strike action is going ahead during the busy festive period.
At the moment fewer than 300 Post Office branches will be affected by the industrial action.
However, many of the branches will remain open to maintain the Christmas service.
Last Christmas posting dates will also not being affected.
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The strike was called by the Communications Workers Union (CWU) after failing to reach a breakthrough with talks, and does not include Royal Mail employees.
According to the Post Office, the CWU has also made comments in the media that they will call further action later next week.
“We had agreed with the CWU that we would resume talks this week, so we are extremely disappointed that it prefers to call for strike action, particularly at such critical time of year,” says Kevin Gilliland, Post Office group network and sales director.
Despite the strike, more than 97 per cent of the Post Office’s 11,600 branches nationally will be operating as usual.
“Any action will affect fewer than 300 of our branches, and many of these will be open to maintain services for customers preparing for Christmas,” said Mr Gilliland.
“We have robust contingencies that will ensure that all branches have the support and cash they need to operate,” adds Kevin.
“Experience tells us we can manage this effectively and minimise the impact on the communities who rely on our services.”
“It will be business as usual in almost all of our network, with over 50,000 Post Office people on hand to support customers as they make their preparations for Christmas,” says Kevin.
Tuesday 20 December is the latest recommended posting date for people sending cards and packages second class via the Royal Mail, and Wednesday 21 December for first class.
To find out which branches will be affected by the industrial action, visit www.postoffice.co.uk.