When Michael Bateman tried to find out why the rice he cooked didn't taste right any more, he stumbled upon a tale of international fraud

Something was wrong with the basmati rice, and I didn't know what. As a cook, your first instinct is to blame yourself. When your bread doesn't rise, you tick off possible human errors, such as temperature and timing. You may not think to blame the flour.

Something was wrong with the basmati rice, and I didn't know what. As a cook, your first instinct is to blame yourself. When your bread doesn't rise, you tick off possible human errors, such as temperature and timing. You may not think to blame the flour.

And so it is with rice. When it turns out soggy and unappetising, you ask yourself, did I wash it well enough to get rid of the starch? Did I add too much water? Did I overcook it?

You don't immediately say there's something wrong with this rice - especially when you've been buying the same variety, year in year out.

The first time I encountered basmati was in the company of an Indian journalist in a Soho curry house. She looked at the rice set down in front of us and asked the waiter indignantly: "What rice is this?" "Patna," he said. "Take it away immediately and bring us basmati," she ordered. She turned to me. "Patna is so plebeian."

Plebeian? Did the caste system extend to grain? Not wishing to be thought plebeian, I made the switch. A good move it turned out to be, for the grains are sweeter, nuttier and fluffier than patna and, to me, the perfect foil for runny curry sauces.

So, basmati can be thought of as the champagne of rice. I buy mine from my local Asian shop. I don't always buy the same brand, and for years I've used the absorption method advised by Indian cooks. (For the record, that is: measure 100g/31Ž2oz of rice per person, wash it to rinse off the starch, put it in a saucepan with 170ml/6fl oz water, per 100g/31Ž2oz, bring to the boil, cover - making a tight seal with crumpled foil if necessary - and simmer on lowest heat for 12 minutes. Raise heat briefly, then turn off and leave undisturbed, lid on, for 12 minutes.)

In this way, I've always turned out perfect dry, fluffy rice. But suddenly it wasn't working. It was softer, stickier, plainer; indeed, more like patna.

Back at the Asian shop, they suggested it was new stock and, like any crop, not always consistent. I bought another pack, from a different supplier - but the results were no better. Asking around, I found that others had had similar experiences. It was then that I discovered I had become a victim of the great basmati rice scam.

It's a fraud apparently well-known in the industry, and even to the British government. Just as fraudulent dealers bulk up Darjeeling tea with inferior leaves, for some time now unscrupulous traders have been passing off inferior grain as basmati or adulterating it.

I contacted the Rice Association, a branch of the Food & Drink Federation, to hear that the Ministry of Agriculture exposed the scam over a year ago. Samples of 41 basmati rices were sent to Nottingham University, where the DNA "fingerprints" were compared with those of authentic basmati. No fewer then 19 samples were found to be adulterated.

Tilda, a leading rice importer which buys direct from the Punjab through its own agents, was responsible for seven of the 22 authentic basmatis in the test. David Robinson, Tilda's technical manager, explained why other buyers, which often have little control over their agents, face difficulties. "In India and Pakistan they can mix in other rices, such as pseudo-basmati crossbreeds. It's difficult to detect because the rice looks similar, but it's cheaper, and it's certainly not grown by the labour-intensive methods used in the Punjab."

Both the Indian and Pakistani governments are looking to create protection for the pure lines of basmati, especially after the Americans took out a patent three years ago on a pseudo-basmati strain in Texas, dubbed Texmati.

More knowledgeable now, I swapped notes with the owners of the shop where I buy my basmati. They too had noticed changes in texture, but had put it down to variations occurring between one local crop and another. They had been checking out their sources and had themselves switched to Tilda for their home cooking.

India and Pakistan need to act to protect true basmati rice. If we continue to buy a product claimed to be basmati which manifestly is not, soon we will stop buying it at any price.

This recipe is from the charismatic film producer Ismail Merchant's enchanting book, Passionate Meals (Hyperion, £9.99). An enthusiastic entertainer, he offers a party-sized biriani, but the recipe can be scaled down.

Merchant has a failsafe way of making plain boiled basmati. Wash thoroughly, then leave to soak in fresh water for 30 minutes. Put to drain in a sieve for 30 minutes. Put the rice in a saucepan, cover to a depth of half an inch and bring to the boil. Cover and cook on lowest flame for 20 minutes. Leave to rest covered for 10 more minutes.

Ismail Merchant's biriani

Serves 14

2 large cardamom pods (black or green) 6 cloves 1Ž2 teaspoon each ground cinnamon (or 1cm/1Ž2in cinnamon stick) and cumin seeds 80ml/3fl oz vegetable oil or ghee 6 medium onions, thinly sliced 3kg/6lb chicken, skinned and cut into 7cm/3in pieces 1 medium garlic clove 1cm/1Ž2in fresh ginger root 1 teaspoon each ground red pepper, cumin powder and turmeric 2 large or 3 medium fresh whole green chillis 500ml/16fl oz plain yogurt 1kg/2lb basmati rice 6 medium potatoes, boiled, quartered and deep-fried 250ml/8fl oz tomato juice 1 teaspoon saffron powder in 250ml/8fl oz milk

Pound together cardamom, cloves, cinnamon and cumin. Place 50ml (2fl oz) oil in a heavy-based pot. Add the spices and half the onion. Fry, stirring, until the onion turns a brownish-gold. Add chicken. Fry for two minutes.

Grind the garlic, ginger, pepper, cumin and turmeric into a paste. Add to the pan. When the fragrance of the spices starts to rise, add half the yoghurt. Stir briskly. Cover pot and tenderise over very low heat for about 20 minutes, checking frequently. If the meat starts falling off the bone, that's OK. Add water if needed; the liquid should be level with the top of the meat without covering it, and should have the consistency of a thick sauce.

Boil the rice until not quite cooked. Leave in a colander.

Put remaining oil in a fresh pot. Add a layer of rice then a layer of chicken, potatoes, remaining onions, tomato juice, remaining yoghurt. Top with rice. Pour over saffron if using. Cover pan with a clean tea towel and replace lid. Leave on a very low heat for about 25 minutes. Serve with raita and an onion and tomato salad.