The Environmental Protection Agency (EPA) has said that water scheme operators which fail to comply with basic standards should be prosecuted for providing water unfit for human consumption.
The recommendation comes after the EPA's latest drinking water quality report found that one in four private rural water schemes was contaminated with animal or human faeces. The water quality in private schemes was of "exceptionally poor quality".
The annual drinking water quality report for 2003, to be published today, finds there has been little improvement in water quality for group water schemes, which provide water to over 200,000 homes.
"It is unacceptable that in 2004 a significant proportion of the population is still receiving water that is unfit for human consumption," the report says.
For the first year, however, the report separated private group water schemes from "'public" group schemes which are run by the local authorities.
Less than 4 per cent of the public schemes were seriously contaminated, the report finds.
Just over 25 per cent of private group schemes were found to have some level of faecal contamination, while 36.5 per cent had some level of bacterial (coliform) contamination.
These rates are only a small improvement on the 2002 figures, even though there has been record levels of investment in water treatment facilities.
This contrasted with large public water schemes which had a 98.7 per cent compliance rate in terms of faecal coliform contamination.
The level of compliance varied greatly across the country. Sligo County Council's private schemes had the worst level of contamination with nearly half of the 15 schemes being contaminated.
The council is upgrading these schemes in a project due to be completed by next June.
But counties such as Westmeath, Kildare and Longford had 100 per cent compliance records for their private schemes.
While overall drinking water quality was good, European regulations which came into force last January, put strict standards on water quality, and required each negative test result to be investigated.
The report says improvements in group water schemes will have to be accelerated to meet these new standards. "The exceptionally poor quality of [ private] group water schemes is clear for all to see," it says.
The report states that local authorities also have powers under the new regulations to issue directions to schemes with poor water quality.
If the managers of the scheme fail to make the improvements, the scheme operators can be prosecuted in the District Court.
Mr Jim Moriarty, one of the report's authors, says the high contamination levels of the private water schemes was "a major concern."
He says that because of the record levels of investment in water infrastructure, there was no valid explanation for any water scheme to be contaminated with animal or human waste.
"There isn't really any excuse. "There are sufficient financial packages available, although it is difficult in fairness to upgrade single schemes one by one."
While the report finds that public water quality was generally good, it says there was "a significant number of water schemes that are supplying water of insufficient standard".
It highlighted problems with colour, nitrate and aluminium levels.