Post Office workers will go on five days of strikes in the lead up to Christmas amid an ongoing dispute over jobs, pensions and branch closures. The industrial action starts on Monday 19 December and will include Christmas Eve.
The Communication Workers Union (CWU) said that the action would involve thousands of workers from the Crown Post Offices, which are often the larger branches on UK High Streets.
CWU assistant secretary Andy Furey said that the company had launched an "unprecedented attack on the jobs, job security, and pensions" of their workers.
While the Post Office say that despite the walkout "at least" 97% of its 11,600 branches would not be affected.
Furey said: "All of the blame for this unfortunate turn of events is 100% down to the intransigence of the company, who have launched an unprecedented attack on the jobs, job security, and pensions of thousands of hard-working and loyal Post Office workers.
"Our members want the Post Office management to pause its closure and privatisation programme, hold off on its planned pensions changes, and commit to sitting down with us and with the other key stakeholders of this Great British institution and, together, construct a lasting vision.
"We want to work together to build a positive future for the Post Office, its workforce and, of course, the people who we serve. The CWU can be a constructive partner to work with, but sadly, the people currently running the company have, so far, chosen the path of conflict and industrial disputes."
But the Post Office say that their cost-saving actions over the last four years had meant the modernisation of almost 7,000 post offices and added more than 200,000 extra opening hours per week.
Kevin Gilliland, the Post Office's network and sales director said: "We want to reassure customers that if further strike action takes place next week, at least 97% of our 11,600 branches will not be involved. 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."
In April 2016, the Post Office announced radical plans to move 61 branches inside WHSmith stores. The company said that the decade-long plans would cut costs and save money to safeguard "the future of the network".
In October this year more than 3,000 Post Office workers staged a 24-hour strike to protest against job losses and management's decision to close a final salary pension scheme.
In a statement the CWU general secretary Dave Ward said it would propose getting the Post Office to the table for negotiations.
"Our members are being forced into fighting to save their jobs and this great institution from terminal decline. We are defending the very future of the Post Office in this country."