The European Commission will issue a final legal warning to the Government today over its failure to abide by EU law and provide clean water supplies to citizens.
It will also threaten Ireland with multimillion euro fines for ignoring two previous rulings by the European Court of Justice (ECJ) over polluted drinking water supplies.
In a legal notice, due to be published today, the commission concludes that more than half of private group water supplies in Cavan, Kerry, Leitrim, Mayo, Donegal and Sligo breached the EU's e.coli standard in 2005.
It pinpoints animal waste, defective septic tanks and the absence of proper treatment as some of the causes of the high levels of e.coli bacteria, which is a primary cause of human illnesses.
The commission says it is taking the new legal action because the Government has failed to fully comply with a 2002 ECJ ruling requiring drinking water supplies to be free of e.coli bacteria.
It is also sending Ireland a similar warning for failing to comply with a 2005 ECJ ruling requiring more controls on polluting discharges to surface water by local authorities, according to the notice seen by The Irish Times.
"I am concerned that, more than four years after a court ruling, and despite substantial Government investments, a significant number of local authority and private water supplies still show a presence of e.coli," writes EU environment commissioner Stavros Dimas. "This needs to be resolved without further delay."
In a significant legal move the commission has also threatened to ask the ECJ to impose financial penalties on Ireland if its responses are deemed "unsatisfactory".
While the potential liability is impossible to estimate, last year the ECJ fined France €58 million for failing to comply with a ruling on fisheries control systems.
The EU legal action comes just days after 90,000 people living in parts of Galway were asked to boil all drinking water due to a dramatic rise in stomach illnesses.
A meeting of officials of Galway City Council, Galway County Council and the Health Services Executive on Tuesday failed to pinpoint the cause of the concern.
Residents are being advised to continue boiling drinking water until next week at least.
The commission's legal action is extremely critical of Government inaction on dealing with water pollution.
For example, it says Ireland has still not adopted the necessary legislation to set up a licensing system for local authority water treatment plants and collecting systems, to be managed by the Environmental Protection Agency, some 25 years after it became due. The ECJ ruling in 2005 on controls on local authority polluting discharges also required new pollution controls on fish farms, a matter for the Department of the Marine. However, the department has "failed to provide any clear details of how and when the ruling will be satisfied", concludes the commission.
The commission has also decided to refer Ireland to the ECJ for failing to pass legislation that would give citizens the right to easily challenge the legality of public authority decisions on environmental grounds.
Under the EU's public participation directive, all citizens are entitled to bring legal challenges without prohibitive expense.
However, there is one piece of good news provided by the commission, which has dropped its legal action against Ireland over drift net salmon fishing.
This decision follows the ban on the practice passed last year in the Oireachtas.