The Post Office faces further strikes before Christmas as workers plan four days of industrial action over the festive period.
The employees, members of the Communication Workers Union (CWU), will walk out on 23 December, Christmas Eve, New Year's Eve and 2 January.
The union also said it will be balloting staff working in crown post offices in January, asking them to take part in further industrial action.
The CWU said that the pay dispute and the associated job losses currently surrounds the 1,500 employees working in the Admin and Supply Chain, who have been "threatened" with job cuts.
"We will continue with our plans for further industrial action until the Post Office removes the very real threat of compulsory redundancies from negotiations," said Dave Ward, the deputy general secretary of the CWU.
"There are no circumstances under which we would accept compulsory redundancies of workers in the Admin and Supply Chain.
"These workers risk their lives every day to do their jobs. This is a crucial dispute and these workers understand how real the threat of compulsory redundancies is to their futures."
Keith Rann, head of supply chain at the Post Office, criticised the proposed action as "irresponsible and misguided".
"We must make changes to reduce our reliance on public money and sustain our business, and we cannot meet their unrealistic demands for the taxpayer to pay for the continuous employment of people who we cannot find a role for within our business," Rann said.
The Post Office said it is offering the supply team and the administration team a "fair and affordable pay offer" of a 6% increase over three years.