The guidance, drawn up by the Food Standards Agency (FSA) after consultation with stakeholders including The Vegetarian Society and The Vegan Society, will provide criteria for the use of the terms 'vegetarian' and 'vegan' on food labels for the first time.
The FSA estimates that there are 3.5 million vegetarians and 0.25 million vegans in the UK. The guidance is designed to make it easier for these consumers to identify the products that are suitable for them.
It also aims to prevent some common mistakes by companies such as labelling drink or food that has been derived from animal products or fish as suitable for 'vegans' and 'vegetarians'.
"There has been a lot of confusion over the use of the terms 'vegetarian' and 'vegan' on food labels both in the retail and catering sectors," said Dr Richard Harding, head of the FSA's consumer choice, food standards and special projects division.
"The root cause of the problem seems to be the lack of agreed criteria. The guidance aims to improve consistency by providing criteria for the use of these terms in food labelling."
This is becoming an increasingly important issue. Food safety fears have led to the emergence a new market in vegetarian ingredients.
Scares such as BSE in cattle and avian flu in poultry have prompted consumers and marketers to cast about for non-meat alternatives. The UK's Vegetarian Society says that the numbers of vegetarians tend to peak in the immediate aftermath of a animal health scare, but drop back down to prior levels afterwards.
Overall vegetarianism has followed a steady upwards curve over the past decade. A 2002 Datamonitor report estimated that there are around 12 million vegetarians across Europe.
With around a quarter of Europe's vegetarians, the UK is therefore a significant market for non-meat products.
"We all want to know what we are eating and misleading labelling makes it particularly difficult for Britain's three million plus vegetarians and vegans to make informed choices," said Tina Fox, chief executive of The Vegetarian Society.
"In the continuing absence of a definition of these terms in law, The Vegetarian Society sincerely hopes that the FSA's guidance is widely taken up by manufacturers, caterers, retailers and local enforcement authorities."
George Rodger, chair of The Vegan Society said: "As more and more foods have become available in packaged form, vegans have had to become accustomed to reading long lists of ingredients to see whether or not a product is suitable for them.
"The new food-labelling guidance from the Food Standards Agency will make things so much easier. If a product is labelled 'suitable for vegans' in accordance with this guidance, they need look no further."
The criteria for the use of the terms 'vegetarian' and 'vegan' in food labelling are set out in the guidance:
The term 'vegetarian' should not be applied to foods that are, or are made from, or with, the aid of products derived from animals that have died, have been slaughtered, or animals that die as a result of being eaten.
'Animals' means farmed, wild or domestic animals, including for example, livestock poultry, game, fish, shellfish, crustacea, amphibians, tunicates, echinoderms, molluscs and insects.
The term 'vegan' should not be applied to foods that are, or are made from, or with, the aid of animals or animal products (including products from living animals).