Members of Eircom's largest union have voted by almost nine to one for industrial action if the disposal of the Eircell network, or any other business plans, do not meet with their approval. Discussions between Eircom and Vodafone on the sale of Eircell are expected to conclude within the next 10 days.

The outcome of the talks is crucial, not just to the 400 or 500 Eircom employees who might transfer with Eircom to a new company but the 11,000 employees left behind. The value and shape of their Employee Share Option Plan holding in Eircom could be dramatically affected, along with the fortunes of Eircom's other 500,000 shareholders.

The vote by Communications Workers' Union of Ireland (CWU) members showed 5,373 in favour of giving their executive a mandate for industrial action yesterday, with 639 against. The other unions are balloting over the next week and are expected to record similar results.

CWU general secretary Mr Con Scanlon said the union now had a sanction to use if needed when the outcome of the current talks was known. He said it had been made clear to the company that the sanction, if granted, would apply not just in the case of the discussions on the future of Eircell, but other possible deals such as the bid for Eircom's fixed line business from Mr Denis O'Brien's eIsland consortium.

"It gives us a strong hand in our negotiations and we are very pleased with the outcome," Mr Scanlon said. "We are not anticipating we will have to use it but we are now prepared for any eventuality that takes place over the next few months."

The general secretary of the Public Service Executive Union, Mr Dan Murphy, said his union was recommending members to sanction industrial action as well. "Our primary concern is the protection of our members' pay and conditions in any future arrangements," he said.

A major problem for the unions was that they knew little more of what was going on than they read in the newspapers, he said.

The national officer for the Civil and Public Service Union, Mr Derek Mullen, said his members would be voting next week. "We are in talks with the company at the moment on pay and conditions and we must signal to Eircom we have to get those issues right before there can be changes," he said.

A spokeswoman for Eircom declined to comment on the CWU ballot or the state of negotiations with Vodafone. However, informed company sources suggested the negotiations were expected to conclude within the next 10 days.