University of Aberdeen scientists bought raw chicken livers from a typical range of supermarkets and butchers over a two-year period and, after testing in the lab, discovered the bug Campylobacter in 81 per cent of them.

In a study published in the International Journal of Food Microbiology the researchers also reveal that 56 per cent of the types of Campylobacter found in contaminated chicken livers matched the 10 most common strains of the bug found in people with Campylobacter poisoning.

Dr Norval Strachan, a researcher into food safety and epidemiology, at the University of Aberdeen, said: “In the UK there are an estimated 500,000 cases of Campylobacter infection per year of which more than 15,000 are hospitalised and approximately 75 die as a result.

“Although outbreaks - clusters of linked cases - of Campylobacter are not common, last year 14 outbreaks of the bug in the UK were associated with consumers eating chicken or duck liver paté.

“By cooking the livers properly and ensuring good hygiene in the kitchen these episodes can be avoided.

“However some celebrity chefs and many recipes advocate only partially cooking chicken liver to ensure that it is pink in the middle.

“But this is recipe for disaster because there is a very fine line between cooked and undercooked. If it is undercooked, the consequences are severe as Campylobacter can be a very nasty form of food poisoning especially in a young child or the elderly."

Dr Ken Forbes, a molecular epidemiologist studying human pathogens at the University of Aberdeen, added: “Our study brings to mind a large Campylobacter outbreak in north-east Scotland a few years ago in which approximately one half of the 165 people who attended a buffet dinner dance were struck down with the bug.

“The study identified chicken liver paté as the most likely vehicle of infection as its preparation involved the deliberate undercooking of chicken livers by flash-frying.

A separate New Zealand study also showed that 90 per cent of positive Campylobacter chicken liver samples contained the bug in internal tissue and that flash frying might be ineffective at killing all of the pathogen present.

This study was funded by the Food Standards Agency. Dr Jacqui McElhiney, policy advisor at the Food Standards Agency in Scotland, said: “Unfortunately, levels of campylobacter in raw chicken are high, so it’s really important that chefs thoroughly cook chicken livers fully to kill any bacteria, until there is no pinkness left in the centre, even if recipes call for them to be seared and left pink in the middle. It’s the only way of ensuring the paté will be safe to serve to their customers.”