The three-year study, sponsored by the Organic Milk Suppliers' Co-operative (OMSCo), found organic milk contained 68 per cent more omega-3 fatty acids on average than conventional milk.
An OMSCo spokesperson said 14 scientists involved in the research had written to Food Standards Agency (FSA) chairwoman, Dame Deirdrie Hutton. Omega-3s are considered to cut consumers' risk of heart disease, and have been linked with better concentration in children.
The FSA has repeatedly refused to recognise that any organic food products are healthier than their conventional counterparts.
OMSCo said the milk study, conducted independently by the Universities of Liverpool and Glasgow from 2002-2005 and published in the Journal of Dairy Science, is the first to consider a cross section of UK farms over a 12-month production cycle.
Nicholas Saphir, OMSCo Chairman, said: "Over the last few years there has been mounting research confirming the higher levels of Omega 3 fatty acids in organic milk. This latest study clearly shows that the higher levels of these essential fatty acids are a result of the whole organic farming system.
"We believe that the consumer should have access to this information through the FSA."
Another study, carried out at the University of Aberdeen in 2004, found organic milk contained an average 71 per cent more omega-3 fatty acids than non-organic.
OMSCo sells organic milk under its Altogether Better brand, claiming it is higher in omega-3, as well as vitamins E and A, than non-organic rivals.
Organic milk sales have boomed in Britain over the last few years and were 50 per cent higher this July than in the same month last year, according to new figures from the Milk Development Council.
The growth adds to a 91 per cent rise in organic milk sales across the UK in the year up to last November. Organic milk still only makes up a very small percentage of the overall liquid milk market, however.
The debate on whether organic food is more nutritious than non-organic has raged for some time.
The FSA says: "On the basis of current evidence, the Agency's assessment is that organic food is not significantly different in terms of food safety and nutrition from food produced conventionally. The Agency recognises that organic food contributes to consumer choice."