A study by the National Audit Office has found that despite large investments into drinking water supply and sewerage systems, another 332 million euros is needed to bring the nation's waterworks up to scratch.
The office said on its website today that around one billion euros has already been invested into water management since 2000, with most of costs covered by EU funds.
Slightly over 400 million euros from EU funds was allocated to the cause during the last EU funding period of 2007 to 2013, but the total spent was greater - 466 million euros - with the Ministry of the Environment calculating that the initial sum would have sufficed.
But the new study shows a further 332 million euros is needed to meet EU requirements. Half of that sum would come from the union's next budget period of 2014 to 2020, the audit office said, while 167 million will have to be found from other sources.
The Audit Office also found that a number of mistakes have been made in the past, including the overestimation of pollution levels, which led to expensive water management systems being built in places where cheaper alternatives would have sufficed.