By edict of the Ministry of Agriculture, two prices must be shown for nine fruits and vegetables: the price paid to the producer, and the retail price demanded of the consumer. Many supermarkets will add a third label, showing the cost to the shop, including overheads.
Since French shops are already expected to give all prices in francs and euros, the shopper could, in theory, be faced with six different price stickers on a stand of apples or grapes. In practice, there is unlikely to be more than four.
The "double pricing" of fruit and vegetables is a temporary measure introduced by the government to pacify irate farmers. Farm-gate prices for much French- grown produce have fallen sharply this summer (because of large harvests) but the growers say that the shops - especially large supermarkets - continue to charge unjustifiably high prices.
The producer price of peaches, for example, has fallen to 2.80 francs (28p) a kilogram but the consumer typically pays 11 francs (pounds 1.10) a kg.
The double, or triple, pricing is supposed to allow shoppers to avoid price-gouging retailers. It is, however, purely advisory: there are no penalties for shops with high profit margins and only small penalties for shops that fail to supply the new labels.
In theory, the forests of stickers should have been visible from Monday. However, the big supermarkets will not be ready to comply until today or tomorrow, and many small shopkeepers seem to be confused about whether the law applies to them. It does.
"Why not force me also to show the wages of my staff, the cost of electricity and the amount I pay in taxes," said one small supermarket operator in Paris. "At the end of the year, you can be sure of one thing. I will have zero left."
The double-pricing experiment applies only to French- produced apples, pears, grapes, peaches, nectarines, apricots, melons, tomatoes and cucumbers. Jean Glavany, the Minister for Agriculture, hoped it would defuse a campaign of protests by fruit and vegetable growers, especially in the south. But it has been dismissed as useless by the growers and unfair by the retailers.
The supermarkets complain that double pricing gives the impression that the retailer is profiting by the full difference between the two figures. For this reason, they propose to complicate the scheme further by showing three figures: farm-gate price, cost to the shop, and retail price.
It has long been a mystery that France, one of the world's great producers of fruit and vegetables, cannot supply fresh produce at modest prices in its shops. Even allowing for the generally higher quality, most fruit and vegetables cost twice as much as in Britain.
The supermakets say their profit margin on fresh produce is never more than 25 per cent and often no more than 10 per cent. The gap between the 28p and the pounds 1.10 kg of peaches (a 400 per cent increase) is, they say, taken up in middle-men's margins, storage, transport, wastage and shop wages.