The contamination of eight per cent of Irish pork with cancer-causing dioxins was all too predictable. I've spent four years researching the factory farming of pigs to make my new documentary film, Pig Business, and I know all too well that this kind of incident is the consequence of mass production, where animals are treated like car parts.

Machines in a gigantic, production-line system, where "accidents" occur all too frequently, are supposedly more efficient than man in caring for the animals.

This Christmas I served pork to my family, but it wasn't intensively produced. I'm lucky: in my village there's a small farmer from whom I can buy direct. It's no more expensive than quality pork in the supermarket. Because we've cut out the middleman, both the farmer and consumer get a better price.

Not everyone is lucky enough to have a small farmer on their doorstep. But if people were aware of exactly what goes on in some of the huge factory farms, and the dire consequences for animal, human and environmental health, they would surely think twice about buying pork from a supermarket shelf without scrutinising the label.

I know that the labels can be pretty misleading – so much so that the trade union Unite, the biggest union in this country with more than two million members, is campaigning for clearer labelling of the origins of the meat on the shelves.

The union is right in saying that when retailers demand cheaper and cheaper products, they pass suffering and exploitation right down the food chain from the animals to workers and ultimately to the consumer.

It's a system which also puts the small farmer out of business.

I've lived in the countryside all my life, and I see how hard it is for small farmers, not just in Britain, but abroad, too. They are raising farm animals naturally, with straw beds, space to move around and fresh air to breathe. But how can they compete against subsidised, giant-scale corporate farming interests, who drive farm-gate prices down to make massive profits?

Factory farming costs more in so many ways. To make my film, I travelled to Poland, which has a comparatively unspoilt ecosystem. Forty per cent of its people are connected to the land, and 25 per cent of Poles work on labour-intensive, small-scale family farms compared to just 1.5 per cent working on agriculture in the UK.

Now that the corporate giants have moved in to Poland, all that is changing. Vast, noxious lagoons containing hundreds of thousands of tons of pig manure are blighting the land, damaging ecosystems and afflicting workers and local residents with noxious gases.

Within these factories, pigs – curious, intelligent, large animals, born to root and forage – are kept in cramped concrete compartments all their lives, and their mothers are kept in cages so narrow they can't even turn around. They are castrated without anaesthetic, their tails cut off and their teeth chopped down so that they can't take their frustration out on each other. They are so prone to illness that they're often kept on a constant regime of antibiotics. Millions of animals are raised like this all over the world and much of it ends up on supermarket shelves right here in Britain.

Intensive farming, whether here or abroad, isn't just bad for pigs – it's bad for human health. Workers in the Polish factory farms I visited suffer a myriad of illnesses, most common of which are respiratory diseases. Locals who swim in nearby lakes have reported strange boils, and diseased fish that dissolve when cooked. The over-use of antibiotics on the confined pigs encourages "superbugs", antibiotic-resistant bacteria which can transfer to humans.

In the Netherlands, 50 per cent of farmers carry the pig version of the potentially deadly MRSA. In Scotland this year, three people with no connection to farms, contracted the pig strain of the disease.

The factory farming system also destroys human happiness and the health of our society. By bankrupting the small farmer, large-scale intensive corporations destroy a way of life that kept the countryside alive and kept families and communities working together.

Though farmers love farming, they can't survive if their prices are constantly undercut by companies that set up where labour is cheaper, regulations are unenforced and they can mop up huge subsidies.

As it takes 17 calories of oil to put one calorie of energy on our plate, what will happen to Britain if the price of oil goes up, and the supermarkets can't stock their shelves because people on the other side of the world begin demanding their land rights to grow food for themselves rather than sending it to distant markets?

Are we going to let our farm skills disappear? Each farming bankruptcy is one more nail in the coffin of food security on this overcrowded island.

But there is something we can do. We can help take back control of our food economy just by how we shop. The message is simple: if the label doesn't clearly state that the pork is humanely produced in Britain, then don't buy it.

It's time to go to the local family butcher, if there is one – if not, try Big Barn, the virtual farmers' market on the web, www.bigbarn.co.uk. Ask for the unfashionable cuts, the chaps and shoulder and belly that needs stewing.

I try to eat less meat, and I try also to buy meat fed with grass, which is healthier for the animals and for us, being rich in the omega-3 fatty acids that we need. Eating too much meat is not good for us or the planet, as pigs consume feed that is depriving people of the land to grow other crops to fee their families.

Most of all, let's demand clearer labelling of pork in supermarkets, so that it's obvious where the meat is from and how it's been raised. Our government, and the suppliers, will listen only if we use our consumer power and make informed choices when shopping. Then we'll be helping small farmers, our health, animal welfare and ultimately, our life support system, the planet.

Tracy, Marchioness of Worcester, who lives on the Badminton estate in Gloucestershire, is an environmental campaigner, a film- maker, former patron of the Soil Association, former trustee of Friends of the Earth, and a trustee of the Gaia Foundation. Her documentary, True Stories: Pig Business, will be shown on More4 on Tuesday, February 3, at 10pm.To find out more, go to www.pigbusiness.co.uk