Goji berries might look innocuous, but the current craze for this "superfood" – fuelled by the endorsement of celebrities such as Kate Moss and Sir Mick Jagger – could devastate Britain's multimillion-pound tomato and potato crops.

The Government has alerted farmers to the threat after it revealed last week that nearly 90,000 goji berry plants, which can carry diseases that are lethal to other crops, have been illegally imported from East Asia in the past year. Some of the plants have been destroyed but it is feared that most are already in the gardens of goji- berry enthusiasts.

The Department for Environment, Food and Rural Affairs (Defra) has issued a warning to commercial growers, garden centres and gardeners, while the National Farmers' Union has warned that disease carried by the bright red berries could be "devastating".

"There are particular concerns over this," said Chris Hartfield, horticulture adviser to the NFU. "Put simply, because goji plants are part of the Solanaceae family – the same as potatoes and tomatoes – the bugs can travel on the goji plants, then easily move to, say, potatoes, where they debilitate the crop." He added: "The retail value of British tomato production is £150m, and potatoes are worth more than that, so the size of the industry that is under threat is pretty massive. If some bugs were to arrive here, they would be devastating."

The goji berry, also known as Lycium barbarum, contains up to 500 times more vitamin C than an orange, and is native to the Tibetan Himalayas. It has been used for medicinal purposes in China for centuries.

Demand in Britain has soared in the past year after the berry became the latest "superfood" to be endorsed by celebrities and health experts. The Plant Health and Seeds Inspectorate warned there is a "substantial trade" in prohibited goji plants in the UK. Seeds and berries can be imported from anywhere in the world, but only plants grown within the European Union are permitted to be imported to the UK, because they are certified to be free of disease.

"All the time new diseases are emerging and evolving," Mr Hartfield said, "and the reason that we have strict quarantine regulations is to protect British growers."

Defra sought last night to allay farmers' fears about the risks of any major outbreak, saying the chances of widespread disease were relatively low, because of weak connections between amateur gardeners and commercial vegetable growers.

Why Britain loves its superfoods

Gojis The bitter berries contain powerful antioxidants. These absorb free radicals in the body, which are linked to disease and signs of ageing

Blueberries The "ultimate superfood" – a quarter of British households regularly eat vitamin C-rich blueberries; 10m kg are sold each year in the UK

Beetroot After years gathering dust in jars at the back of the pantry, the humble beetroot now has a celebrity following due to its low calorie content

Spinach Popeye isn't the only one who enjoys the nutrient-rich greens. Full of folic acid, iron and vitamin A, spinach can be eaten raw or steamed