The Irish Farmers' Association has again criticised leading supermarkets for using food such as fruit and vegetables as a loss leader.
But supermarkets have reacted angrily to the claims.
The IFA says farmers are being exploited and bullied by supermarkets when special offers are made below the cost of production.
At last week's AGM, the association said predatory prices by supermarkets were one of the biggest threats to farmers.
The IFA says such practices are endangering the remaining Irish potato, vegetable and fruit growers.
Now the IFA has accused four supermarkets of undermining the livelihoods of farmers - Tesco, Superquinn, Aldi and SuperValu.
It says food cannot be used as a loss leader for campaigns designed to entice consumers into supermarkets. While supermarkets maintain their margins, they say, discounts come straight from the farmer's pocket.
IFA President Padraig Walshe said glib advertising slogans, offering 'more for less' every day, are perpetrating a great deceit on the public.
He said the four main groups and the German discounters have a stranglehold on producers and co-ops, who are the real casualties in the wars between them for market share, while they hold onto their profit margins.
Mr Walshe said the weakness of producers and co-ops is epitomised by their fear of being de-listed should they have the temerity to seek a price increase.
But supermarkets and Retail Ireland have completely rejected the claims that farmers are getting a raw deal.
Aldi Stores (Ireland) says its special promotions are providing great value on fresh food to Irish customers, and Aldi is paying normal prices to its suppliers, including Irish farmers and processors with whom it has long-established relationships, for this produce.
Aldi says the cost of the promotion is not being borne by farmers or growers.
SuperValu and Centra have also said they are committed to ensuring farmers get a fair price.
Retail Ireland, the IBEC group that represents the Irish retail sector, has also rejected the IFA's allegations of predatory pricing as groundless.
'If the IFA have any evidence of predatory pricing they should bring it to the Competition Authority immediately',' Torlach Denihan, Director of Retail Ireland, said. 'The IFA ignores the consumer, but the retail sector cannot, as it depends on the consumer for its very existence.
'Retailers compete aggressively to bring best value to the Irish consumer and make no apology for this. The sector is proud of its efforts to secure value for its customers, notwithstanding the IFA perspective that this is something to be ashamed of.'
