The postal workers' union has threatened to continue strike action into the Christmas period unless they can reach a "fair" settlement with Post Office management.
Dave Ward, CWU deputy general secretary, said:
If the Post Office thinks this dispute will simply fade away they are sadly mistaken. The company's plans are to downgrade the network, reduce services to local communities and hit jobs in the network.
Next week's strike and the continuing sales ban activity will continue into the Christmas period unless management see sense and negotiate a fair deal for Crown office staff.
The union said next week's strike will affect up to 4,000 staff in 372 offices.
More top news
George Osborne has said the UK economy is "prepared for the unexpected". So did he overstate his Brexit warnings?
Former Girls Aloud singer Kimberley Walsh is pregnant with her second child, she has revealed.
Chancellor George Osborne will seek to reassure financial markets on Monday morning following Britain's decision to leave the EU.