The Food Standards Agency (FSA) has embarked on an ambitious review of food labelling policy, with expert committees, a Clear Labelling task force, "stakeholder dialogues", consumer and product surveys, and extensive consultation. It is not alone. Throughout the world, governments are drafting national codes and taking their recommendations to United Nations meetings on labelling standards that will ease the way for international trade in food.

Food labels are crucial to manufacturers, advertisers, retailers, governments, regulators and, increasingly, health and environmental campaigners, enabling them to influence consumer choice at that crucial place - the point of sale. Last year, the FSA conducted a national survey which found that nearly 60 per cent of shoppers usually or always refer to food labels, mainly checking the "use by" date, cooking instructions, amounts of fat, sugar and salt, and the use of additives and GM ingredients.

A smaller but growing number of people (significant to manufacturers because they tend to be more affluent) look for information on the way the food was produced - whether by fair trade, with good animal welfare or strict environmental standards.

Many labelling schemes are thorough and well presented. The trouble often occurs when the product doesn't have much to boast about. The labelling of fat content is a good example. We all know that eating a lot of fat, especially saturated fat, is bad for you. In the FSA's survey, 42 per cent of people said they check labels for fat content. Yet there is no legal requirement for this information to be on the label and, unsurprisingly, it is often fatty products that don't carry it.

Misinformation about fat is a particular problem where foods are touted as "healthy" or "healthier". There is one muesli bar that proclaims itself to be "84 per cent fat-free". Put it another way, the muesli bar contains 16 per cent fat. Not quite so appealing, is it? Yet it is marketed through health-food shops and even proclaims "healthy eating" on the label.

What are shoppers supposed to make of this misinformation - particularly when, as the survey shows, many people find it difficult to interpret numbers and percentages?

The law limits the use of the phrase "low fat" to foods that contain less than 3 per cent fat, but this rule is being challenged persistently by the margarine companies, which want to use "low fat" on products that have less fat than a competitor's. But would you expect any margarine (whose main ingredient is fat) to be reasonably described as "low fat"?

These descriptions matter. The government estimates that a third of coronary heart disease and that up to a third of cancers are attributable to diet. As a nation, we eat too much fat, salt and sugar, and too little nutrient-rich fruit, vegetables, complex carbohydrates, lean meat and fish. Food labels are a crucial tool to help people make healthier choices about the food they and their children eat.

The Food Standards Agency has promised to be firm on labelling issues and to put the consumer first. It will have its work cut out, given the examples we regularly come across. Mothers want to buy healthy snacks for their children: bung a picture of some fruit on the front of a jelly sweet packet, add some vitamin C and call the added sugar "added energy for growing kids". Men have heard that olive oil is good for their heart: produce a normal margarine that's 4 per cent olive oil, raise the price and describe it as "healthy" olive spread. Women have read that wholegrain cereals could help reduce the risk of heart disease: carry an advertisement for a heart-health charity on the front of the cereal packet, because there isn't enough evidence to make a direct health claim - the implication will have to do.

FSA meetings usually attract a handful of specialists. But at a recent meeting of the new Food Labelling Forum, hosted by the FSA, hundreds of people - from environmental health offices, local authorities, small businesses, international food companies, trade associations, advertisers, health promotion organisations, consumer groups and health charities - crammed into a room in Westminster.

What must prevail in the discussions and policy decisions over the coming months is the primacy of human health. FSA decisions must support Department of Health initiatives to rebalance our diets. This will be a crucial test of "joined-up" government. We can look to organisations such as the Co-op for ideas - it already highlights own-label foods unambiguously as "high fat", "medium fat" or "low fat". Graphical representations of percentages may also help. We will also need new rules to curb the misuse of fruit imagery, deceptive nutrient descriptions and exaggerated health claims.

The food-labelling review will be one of the FSA's first great tests. For the good of our long-term health, let's hope it gets it right.

Kath Dalmeny writes for the Food Magazine, published by the Food Commission, an independent consumer watchdog (enquiries@foodcomm.org.uk)