Post Office workers were set to strike for five days from Monday of next week.
The five-day strike is an escalation in the CWU union’s fight against office closures, outsourcing and an attack on pensions.
CWU members walked out earlier this year in three separate 24-hour strikes.
With bosses refusing to back down, they are stepping up their action in the week before Christmas.
CWU assistant secretary Andy Furey attacked the “intransigence” of Post Office bosses “who have launched an unprecedented attack on jobs, job security, and pensions”.
Workers are fighting a plan to close some 100 of the main high street post offices and outsource them to companies such as WHSmith.
The selloffs will mean job losses, with new workers in the replacement offices likely to be employed on worse wages and conditions.
Bosses also want to close workers’ defined benefit pension scheme and replace it with a worse defined contribution scheme.
The move means some workers could get thousands of pounds less when they retire