DNA TESTS on 300 bacon products from various supermarkets have found that some 'Irish' rashers were from imported pigmeat.
The IFA accused retailers and meat companies of misleading consumers by using labels that imply their products are Irish.
The Irish Farmers Association revealed that tests had shown that half of them were sliced from imported pigmeat.
Love Irish Food, which is a marketing body for Irish-made products, has said it is "extremely disappointed" with the findings.
DNA tests carried out by genetic specialists Identigen proved the meat did not match the DNA profiles in a database of every boar in the Republic of Ireland, meaning it must have been imported. IFA Pigs chairman Pat O'Flaherty said: "It is unacceptable that companies and retailers are using imported pigmeat in their products.
"Some companies and retailers are relying heavily on imagery and branding that would lead the consumer to believe they are buying Irish," he said.
The IFA said DNA tests on 300 samples of pork and bacon products found that 52pc of the products were not Irish.
The IFA stressed that this was not technically illegal but highlighted bizarre labelling regulations which allow imported meat to be labelled as produced in Ireland if it is cured or processed here.
The label on the packet of Smoked Back Rashers made by J Crowe and Son stated it used Irish pork, gave the country of origin as Ireland and had the Love Irish Food logo – but genetic tests showed the meat was imported.
A spokesperson for J Crowe & Sons apologised last night.
"We apologise unreservedly to our customers for the error made. The product in question is outsourced and as soon as we were made aware of the issues from the IFA we set about rectifying the problem."
The IFA wants changes to labelling rules to ensure the country where the animal is raised is shown on the packet. It said that tests on bacon with the Bord Bia quality assured label had shown this meat was actually of Irish origin and consumers could trust it.