Falling revenues sparked angry protests from French farmers recently with fruit and vegetables being dumped outside government buildings.
Tonnes of tomatoes, peaches, nectarines and melons were left outside offices in the south-western towns of Perpignan and Montauban.
The farmers claim that many big supermarket chains are underpaying them and over-charging consumers to drive up profit margins.
France's economy and finance minister, Nicolas Sarkozy, has suggested imposing a minimum price for producers on wholesalers and supermarket groups.
However the head of the union representing tomato farmers, Pierre Diot, warned such a move would be "suicidal" without state subsidies for unsold stocks.
Sarkozy has suggested tomato farmers be paid 85 euro cents a kilo instead of the 30 euro cents currently obtained on the market.
But Diot said buyers were unhappy with that price, particularly when Belgian and Dutch grown tomatoes could be had much cheaper.
Other fruit and vegetable farmers have yet to strike a deal with the supermarket chains.
There were also questions over whether any price agreements would pass scrutiny by both the French and European competition authorities.
