Members of the Communications Worker's Union have voted overwhelmingly to take industrial action if An Post goes ahead with its plan to close down its parcel delivery service, SDS.
The union has the support of 91 per cent of its members should it persist with the action in response to what it sees as a breach of existing agreements by management.
Yesterday An Post ignored calls from the CWU to defer the closure of SDS, which is scheduled for February 1st, 2005.
Commenting on today's ballot, Mr Sean Mc Donagh of the CWU said: "The overwhelming nature of the result reflects the widespread anger and frustration felt by staff in the company, who no longer have faith or confidence in An Post management.
He continued "The CWU has today declared its intention to defend its members against this incompetent, unprofessional and belligerent management where it continues to breach agreements previously reached. In the event that An Post management breaches any existing binding agreements, the Union intends to act".
The closure of the service will result in the loss of 270 jobs and staff had been given until today to sign up for redundancy, retirement or redeployment.
An Post chairwoman Ms Margaret McGinley said the decision to integrate the service "into core An Post operations" was the correct one.
"The Board has considered issues, raised by the Communication Workers Union (CWU), in relation to the decision taken last July to integrate the SDS business into core An Post operations.
"Following detailed discussion on the matter, the Board concluded that the basis for its decision was sound and that the implementation of the decision must continue in accordance with the timescale set at its July meeting," she added.
An Post claims SDS lost €28 million over the last five years and had no prospect of a turnaround in fortunes.
Members of the CWU protested outside the GPO yesterday, calling for an independent review of the figures used by An Post to justify the closure.
They were joined in their demands by Labour spokesman on communications, Mr Tommy Broughan, who said that conflicting reports on the financial state of the service justified further investigation.
"Minister Dempsey, as the senior representative of the shareholders must now urgently investigate the finances of SDS to clarify the true picture for Dail Eireann," said Mr Broughan. "Pending that investigation, the so-called 're-integration' of SDS into An Post must be halted."
The union will also continue to monitor An Post's proposals for the Collection and Delivery area which it claims would have a devastating impact on customer services.