The Food Safety Authority has confirmed that a survey in 2007 found that 1% of samples of bottled water had E. coli.
6.3% of water was found to have coliform bacteria, indicating possible faecal contamination.
On RTÉ News at One, FSA Chief Specialist in Food Science Wayne Anderson said the level of contamination was unacceptable and any problems found were corrected immediately.
He said consumers should not be concerned about the quality and safety of bottled water on the market today.
It was found that one in every 11 of Irish produced bottled water was contaminated, compared to one in 119 of imported water.
The study also found that over 7% of bottle water was in breach of Irish or EU guidelines.
