The illicit and highly-lucrative trade in shellfish is putting the health of many thousands of people at risk with tonnes of potentially contaminated seafood feared to be entering the food chain.

The Independent reports UK health officials and food watchdogs are concerned that a boom in the illegal harvesting of cockles, clams and oysters for sale to restaurants and wholesalers threatens outbreaks of serious food poisoning.

The thriving seafood rustling industry, which sees unlicensed gangs of pickers target beaches and mudflats across the country to steal molluscs worth thousands of pounds at a time, has prompted a crackdown by the authorities.

But with some pickers operating in organized gangs, fisheries protection bodies say they lack the resources to effectively tackle the problem.

With an annual value of at least £250m, the legitimate shellfish industry is a major part of Britain’s food economy. Properly gathered molluscs are subject to strict purification treatments, including ultra-violet light and filtering, to ensure they are fit for human consumption.

But shellfish taken from prohibited or unclassified fishing grounds, or sold before being properly treated, put the public at risk of serious illness caused by E. coli, norovirus, and salmonella, which can all be found in contaminated molluscs.

An investigation by The Ecologist and The Independent has been told that in the event of a major health scare, the illegal trade would make it difficult for officials to verify the origin of some shellfish despite strict documentation procedures which are supposed to ensure traceability of all consignments of shellfish moved or sold on a commercial basis.

The Food Standards Agency (FSA) said it received “regular” reports of illegal shellfish harvesting and warned of the risks it poses to consumers.

Highly-organised gangs, some believed to be operating directly on behalf of fish merchants, others run by gangmasters, are known to have targeted shellfish stocks in Sussex, Hampshire, Dorset, Merseyside, Lancashire, Cumbria and Teeside, amongst other areas, in recent years. Parts of north Wales and Scotland have also been affected.