UK officials say they will defend food producers' right to label groceries by number, amid fears that the EU may consign "a dozen" eggs to history.
Efforts to standardise food labels across the 27-nation EU have gained momentum with new draft legislation going through the European Parliament.
MEPs backed labels indicating weight or volume, but rejected labels that just show the number of items in a pack.
A UK minister said the EU should allow shoppers to "buy eggs by the dozen".
"We know what customers want. They want to buy eggs by the dozen and they should be allowed to - a point I shall be making clear to our partners in Europe," said UK Environment Secretary Caroline Spelman.
Conservative MEP Syed Kamall warned that "millions of pounds could be wasted by shops and bakers having to change packaging just to comply" with the new legislation.
Too many cooks?
EU countries currently have exemptions allowing some pre-packed foods to be labelled by number alone - for example, a dozen eggs or four bread rolls.
The UK online trade magazine The Grocer warned that the legislation "could even see special unit-based promotional packs offering 'eight chocolate bars for the price of six' banned".
Earlier this month MEPs adopted numerous amendments to the new European Commission directive on food labelling.
The legislation will now be considered by EU government ministers before a second reading in the parliament. Agreement on a final text could be reached by the end of this year.
The Labour Party leader in the parliament, Glenis Willmott MEP, voiced regret that in its current form the legislation would not allow some products to be sold simply by number.
The parliament rejected an amendment which said: "In the case of foodstuffs normally sold by number, member states need not require indication of the net quantity provided that the number of items can be clearly seen and easily counted from the outside or, if not, is indicated on the labelling".
The UK Federation of Bakers says selling baked goods by measuring and not number would require bakeries to spend large sums on new weighing equipment. It says customers understand that "no two rolls are the same".
But Ms Willmott said the draft did not explicitly rule out selling groceries by number, and added: "We fully expect the exemption to be in the final version".
A Danish MEP closely involved in the negotiations, Christel Schaldemose, also defended the current national exemptions.
"We still have different cultures for food in Europe - we should allow member states to do something specific," she said.
Labels showing both weight and number would be the best solution, she told the BBC.
Another "problematic" area is the definition of a "portion", she said. When Danish shoppers were asked to define a portion of cornflakes, she said, none of their guesses matched Kellogg's 30g portion.
"A portion needs to be scientifically based - there is a risk of misleading consumers," she said.