Stormy weather has led to more than 5,000 reported faults being reported to telecom network provider eircom.
More than 2,000 new faults were reported on Monday and a further 2,000 yesterday.
The worst affected areas are the northwest (Donegal, Sligo, Mayo, Galway), the southwest (Cork, Kerry and Limerick) the northeast (Louth, Cavan, Monaghan) and the southeast (Waterford).
"Our repair crews are working to repair faults as quickly as possible," said a statement from eircom.
"We will also have crews working throughout the weekend to restore service to as many customers as possible.
"Customers are reminded that they can log faults on the “Log a Fault” section of our website (www.eircom.ie) or through our automated customer service line 1901. Faults can be reported to either service 24 hours a day, seven days week.
"We would like to assure all of our customers we are making every possible effort to restore service as soon as possible and we will provide further updates in the coming days."