More than 600,000 people in Dublin, Kildare and Meath are affected by the boil water notice.

The EPA's environmental enforcement office director Dr Tom Ryan said the increased legal support may be necessary in light of two boil water notices affecting at least 615,000 people in the greater Dublin area over the past fortnight.

Irish Water’s managing director Niall Gleeson has described the company’s efforts to refurbish the old Leixlip water plant as being like “trying to change the tyres on a car while it is still heading down the road.”

Several alarms at the Leixlip Water plant “were not responded to”, leading to the country's largest-ever boil water notice last month, TDs will be told tomorrow.