The country is bracing itself for more heavy rains as flood relief workers called off a planned strike to deal with the devastation wreaked on parts of the country.

Environment Minister John Gormley said it would not be possible to gauge the full scale of the damage in Cork, Galway and Clare until the middle of the week.

"Things are very bad," he said. "I think it's fair to say what we are experiencing at the moment is unprecedented."

Mr Gormley and Taoiseach Brian Cowen thanked council workers who agreed not to take part in Tuesday's national public sector strike because of the crisis.

As many as 2,000 staff involved in the frontline of the emergency response, including support workers at the Mercy Hospital and St Finbarr's Hospital in Cork, will continue working.

Speaking after a meeting of the government's Emergency Response Co-Ordination Committee, Mr Cowen warned high tides and further heavy rainfall were being forecast for Monday and Tuesday.

Half of all homes in Cork city are expected to remain without tap water for at least a week after massive damage was caused to the city's main pumping station. Schools without a water supply have been told to shut down. Tankers are distributing water at emergency supply points for areas worst affected across the city.

Hundreds of people evacuated from their homes in Ballinasloe, Co Galway and Ennis, Co Clare, have not been allowed to return to their homes.

The Defence Forces have been deployed to some of the worst hit areas to help local emergency services, and remain on high alert should conditions deteriorate.

Fears of water pollution has seen boil notices in parts of Cork and in Galway.