The Food Safety Authority of Ireland has called for the sale of unpasteurised raw milk to be banned after tests showed harmful bacteria.
Some 7pc of raw milk samples tested positive for listeria, while 3pc were found to contain campylobacter, according to a new report by the FSAI.
Listeria - a bacteria found in soil, water and some animal products - can pose a major risk of illness to vulnerable people, with unborn babies at risk of stillbirth if a pregnant woman ingests it.
Campylobacter is the most common form of bacterial food poisoning in Ireland. Although it normally clears up after a few days it can kill vulnerable people.
The results were even worse for samples taken from milking equipment filters which trap large particles such as faeces in milk - some 20pc of these were found to be contaminated with listeria and 22pc with campylobacter - both of which can cause fatal food poisoning in vulnerable individuals.
Salmonella was detected in 0.5pc of raw milk sample and in 1pc of milk filters, while E coli 026 was found in 6pc of filter samples, according to the survey of 600 samples from 211 farms.
The Department of Agriculture proposed banning raw milk sales a few years ago but rowed back after a vociferous campaign by top chefs and food writers including Darina Allen of Ballymaloe House to keep it on the shelves. Advocates argue that raw milk can be beneficial in boosting the immune system and helping protect against allergies and asthma and that other countries allow its sale with regulations to minimise risks to consumers.
However, the FSAI said yesterday its new report showed that raw milk can contain harmful bacteria so drinking it increases the risk of developing food-borne illness.
"The FSAI continues to recommend that the sale of raw milk for direct human consumption should be prohibited in Ireland and advises that the most effective way to protect public health is to ensure that all milk is effectively heat-treated (eg pasteurised or boiled)," it said.
This was particularly important for infants, children, pregnant women, older people and those with a weakened immune system or chronic illness.
FSAI director of food science Dr Wayne Anderson said that almost all milk sold in Ireland was pasteurised, which is the most reliable way of ensuring it is safe to drink.
"While the market for raw milk is small, it remains a serious concern given the well-documented public health risks posed by the presence of pathogens in raw milk," he said.
The FSAI recommended that consumers avoid raw milk, but said they should at least boil it first to kill any harmful bacteria.