There is Death in the Pot, A Treatise on Adulterations of Food and Culinary Poisons, was a bestseller in the early 19th century. Manufacturers have always cut corners and substituted cheap alternatives for expensive ingredients, but the first great age of food adulteration came with the industrial revolution. Urbanised populations, removed from the land, not only required new supply systems but were also largely ignorant of how their food was made. Whereas before then, an unscrupulous local butcher or baker might have been restrained by the knowledge that any shortcuts he chose could poison his neighbours and friends, now he could hide in the anonymity of distance and the city.

Analytical chemistry was in its infancy, but as it developed it became possible to detect adulterations, and a scandal in the making. Red lead was being used to colour cheese; beans, alum and gypsum were being used as substitutes for malt and hops in beer; acorns were bulking out coffee; chalk and clay were added to flour.

Chemists Frederick Accum, author of the treatise, and John Mitchell, led a campaign to expose the routine nature of adulteration together with a number of doctors, including Arthur Hassell, in a series in the Lancet. Their work led to the 1875 Sale of Food and Drugs Act, which made it an offence to sell debased food, but not before Accum had been forced to flee the country. The food industry's arguments at the time have a familiar ring to them. People wanted cheap food, the poor couldn't afford anything else, if they didn't like it they wouldn't buy it and, besides, the added ingredients made it look and taste better.

With each generation, the adulterations have changed but the elements have followed a pattern: ignorance among the consuming public, an assumption among the producers that what they are doing is entirely acceptable, and the lure of large profits.

Sylvia Pankhurst gave as an example of sweated labour in her 1931 book, The Suffragette Movement, the work of women whose job it was to rub minute pieces of wood into seed shapes so they could be added to raspberry jam made without the aid of raspberries. Outraged, she opened a factory making jam from real fruit at affordable prices to create jobs for pacifist women during the first world war.

After the second world war, fruit squashes entirely devoid of real fruit, were made with sugar, citric acid and flavours. Starch was added to give the impression of cloudiness created by fruit, chopped cellulose imitated pith, and tiny bits of wood were made to look like pips.

The legalised adulteration of 21st century food may be an altogether more hi-tech affair but it adheres to the pattern. Millions of pounds are spent on scientific research to turn cheap ingredients into "added value" foods. Nearly $20bn a year is spent by manufacturers on food additives to change the colour, texture, flavour and shelf life of products. Over $1bn a year is spent on food colourings alone, to deceive our senses while we maintain our state of blissful ignorance.

Who is supposed to protect us from these adulterations today? Responsibility for food is divided up between different government departments. The old Ministry of Agriculture, Fisheries and Food, long criticised for being more concerned with the interests of the farming industry than the public, was abolished after the foot and mouth crisis and absorbed into the new Department of Environment, Food and Rural Affairs. The food bit was, however, only added to the new department's title at the last moment, according to senior civil servants.

Defra is reponsible for food supply and one of its stated aims is "to promote a sustainable, competitive and safe food supply chain which meets consumers' requirements". But the burden of its responsibilities lie more in protecting the environment and making agriculture sustainable, than in nutrition standards.

The Department of Health has a role, and though the secretary of state tends to concentrate on sickness rather than health, the junior minister of public health, currently Hazel Blears, is supposed to take care of nutrition. The department is beginning to take some interest in the relation between heart disease and cancer and diet, but its focus is still largely on advice - eat more fruit and vegetables, cut down on salt - and has done little to address adulterations of processed food with fats and sugars.

The Food Standards Agency was set up in 2000 after the BSE crisis, in recognition of the need for an independent body to protect the public interest in food. Its objectives are "to reduce foodborne illness, help people eat more healthily, promote honest and informative labelling, promote best practice within the food industry, and improve enforcement of food law".

In practice, its accounts for last year show that it spent about 60% of its budget on food safety, and just 10% on nutrition and the quality of diet. Its line tends to be that, so long as something is properly labelled so that consumers can make a choice, it's OK.

One of the problems is the way the law has evolved. The adulterations which we have outlined are not only all perfectly legal but are enshrined within the law. The amount of water you can pump into a ham, for example, or the minimum amount of meat in a sausage is all laid down in the regulations. To complicate things further, enforcement of breaches of food legislation is mostly carried out at local authority level - by trading standards on labelling, and by environmental health officers on hygiene.

While manufacturers are fixing at a global level, enforcement is left, poorly resourced, to struggle along at a local one.

At the European level, the new European Food Safety Authroity is just being set up, but an outline of its responsbilities by consumer protection commissioner David Byrne makes clear that safety, hygiene, labelling, and new technologies are the priorities.

No one seems much concerned with whether we are all sold junk. Any campaign to stop routine adulterations is likely to have to come, as it has done in previous centuries, from the ground up.