An Post was yesterday served with two weeks' notice of industrial action after postal workers voted to strike in pursuit of a pay claim.
Minister for Communications Noel Dempsey condemned the strike threat and warned that he might respond by removing the company's letter post monopoly earlier than planned.
The strike notice was served by the Communications Workers' Union (CWU) after members balloted overwhelmingly for industrial action.
It said 90 per cent of its 8,500 members had taken part in the ballot, and 90 per cent of these had supported the decision to strike.
The union did not say what type of industrial action would take place initially, but the ballot gives it a mandate to stage an all- out strike.
The company and the union traded insults yesterday after the ballot result was confirmed.
CWU general secretary Steve Fitzpatrick said the union would defend its members against an "incompetent, unprofessional and belligerent management" that had "wreaked havoc with the national postal service".
An Post said it had been forced to confront a "serious onslaught of lies, service sabotage and obstruction" by the CWU.
"This utterly cynical action is specifically designed to damage the company, its business and its reputation," it said in a statement.
The strike threat is over the company's failure to pay the full terms of the Sustaining Progress partnership deal to staff and pensioners.
Workers are owed an additional €30 a week under the deal, while pensioners should be receiving an extra €15, the union said.
In a 65-page recommendation in July, the Labour Court said the increases should be paid, but only after the union had agreed to a major rationalisation of the company's collection and delivery service.
The recommendation was accepted by an An Post but rejected by the CWU, which said the Sustaining Progress increases and the planned rationalisation are separate issues and should not be linked.
The union claims that the 4,500 workers affected by the rationalisation are being unfairly pressurised into accepting "highly detrimental" changes, so that 6,000 colleagues in other areas of An Post receive a cost-of-living pay increase.
This argument appeared to cut little ice with Mr Dempsey yesterday. He said the sooner the union accepted the Labour Court's recommendation the better it would be for the company and its workers.
Mr Dempsey confirmed that if the strike went ahead, the Government would consider removing An Post's letter post monopoly in advance of the 2009 deadline set by the EU.
"Action such as what the CWU appear to be proposing now is only going to accelerate [the removal of the monopoly]," he told RTÉ's News at One programme.
Mr Fitzpatrick said members of the union would not be "bullied" into relinquishing their rights by Mr Dempsey's threats to open up the service.
Labour communications spokesman Tommy Broughan TD said employees "never easily opt to go on strike" and called on Mr Dempsey to intervene immediately.
He claimed management at An Post had allowed a poisonous industrial relations climate to develop.
The strike threat was condemned by business groups including the Small Firms Association, the independent business body ISME and the Chambers of Commerce of Ireland.