Reported in the daily newspaper The Independent, the study by the Food Standards Agency of nearly 300 samples of rice sold in a range of outlets from supermarkets to corner shops found that nearly one in five packets had more than 20 per cent of non-basmati rice. In one in 10 cases, the adulteration reached 60 per cent.
A spokesman for the agency said: "Basmati rice ... is a premium product and therefore attracts higher prices than other long-grain rices. Telling the difference between them is difficult, and there is a profit to be made from mixing in a cheaper variety. The industry code of practice is out of date and there is a need for new standards."
Basmati is the name given to certain rice varieties grown exclusively in the Himalayan foothills in north-west India and Pakistan. The rice, which has grown in popularity in the UK during the past 10 years, has a distinctive aroma and its cooked grains have a characteristic elongated shape. But the term 'Basmati' is not protected in law.
However, a new guidance launched by the FSA in February this year, and which underpinned the recent basmati investigation, recommends that the term 'Basmati' should only be used to refer to 11 Indian and five Pakistani rice varieties which display typical Basmati properties. The list may expand as new varieties which conform to the same criteria come onto the market.
The guidance also recommends that the country of origin should be listed and consumers should be told if the rice is mixed with grains from non-Basmati varieties.
Contamination of crops is not a new problem, and has led to a series of tools that food makers, regulatory bodies and processors can use to detect any irregularities in food products.
Earlier this month, scientists in the UK said they had developed a reliable DNA screening method for identifying adulteration in basmati rice, increasingly important at a time when certain varieties are attracting premium prices.
Researchers from Reading Scientific Services Ltd (RSSL) said that they had developed the screening method - which has been validated on all of the commercially available varieties - to allow both suppliers and consumers to have more confidence in the accuracy of product labelling.
According to the organisation, its screening method would give rice importers a quick and reliable means of authenticating their supplies - the screening method can detect the presence of other rice varieties mixed with basmati, and to distinguish between the different varieties of basmati.
Since some varieties of basmati rice attract a premium price, and are labelled accordingly, the DNA screening method will help the industry to label its rice products accurately.
"Although some mixing of rice species is permitted, those suppliers seeking to provide a premium product will welcome the assurance that this method gives in verifying that their supplies are 100 per cent pure," said Dr Andrew Tingey, head of the molecular biology laboratory at RSSL.