Published Friday, 23 October 2009
It follows strike action from sorting staff - including those at Mallusk - on Thursday over pay and modernisation.
The Communication Workers Union has said there will be three more walkouts next week.
Peter Bunting from the Irish Congress of Trade Unions said: "It's important to press upon the government, particularly at Westminister and with Peter Mandelson, that workers are very serious about seeking a fair and just working system - and to oppose the privatisation of Royal Mail, which is really in the public interest."
Royal Mail Managing Director, Mark Higson, said he was appalled by the decision to continue with further strike action.
He said: "Any pretence from the CWU that they care about customers or about the future of the postal service is now shown to be totally dishonest.
"The CWU leadership has failed to honour and deliver the agreement we both negotiated on Tuesday night that would have averted this week's strikes, ensured no further strikes until the end of the year - and given both parties a period of calm for further talks and to give customers the service they deserve between now and Christmas."
Royal Mail has also said that its door is still open to sign that agreement.