Published Tuesday, 27 August 2013
Workers based in the larger branches will strike on Tuesday. (© Getty)
The workers who are taking action are based in Crown Post Offices - there are approximately eight in Northern Ireland.
Communication Workers Union (CWU) members in England and Wales will also walkout. Staff in Scotland stopped working on Monday as the bank holiday is not in effect there.
The dispute is over plans to franchise or close over 70 'Crown' post offices which are the larger high street branches owned by Post Office Ltd.
CWU Deputy general secretary Dave Ward said the union is prepared to take prolonged action over "management's slash-and-burn approach" to improving the business.
"This is a company which made £94m profit last year and paid out £15.4m in bonuses to senior managers," he said.
"It's a clear case of double standards and trampling those at the bottom for the benefit of those at the top."
Kevin Gilliland, network and sales director at the Post Office, said they were extremely disappointed by the union's decision to take further action - this is the eleventh time staff have been on strike.
"This action can only cause disruption to customers, cost our people money and place further pressure on the Crown network which is currently losing £37m a year.
"We must continue with our plans to turn around the Crown network to ensure we keep these branches on high streets and in city centres across the UK.
Mr Gilliland said they remained open to discussions with the union.
It comes on the same day Royal Mail said it delivered a "target beating performance" in the region between April and June, with 94% of First Class mail delivered on time.
Delivery drivers are not involved in the industrial action.
© UTV News