UK government safety advisors have warned that extensively farmed chickens are not necessarily safer than those that are intensively farmed.

A working group investigating ways to reduce the presence of the common food poisoning bug campylobacter, has said that the bug is more likely to develop in extensively farmed birds, partly because of their longer life span.

The Food Standards Agency has yet to comment on the report but organic campaigners already fear that it will be used to promote intensive farming practices.

Richard Young, policy adviser for UK organic campaigners the Soil Association, told the Guardian: “No scientists have yet looked to see if the higher levels of campylobacter in organic poultry … relates to pathogenic or benign strains.”

Campylobacter is responsible for around three-fifths of the 100,000 proven food-poisoning cases each year in England and Wales. Poultry is thought to be one of the main sources of the bug. Proper cooking of the meat should ensure that the bacteria is destroyed.