A warning has been issues to shellfish pickers in the River Teign and Exe over the health risks and the importance of sticking to the areas where it is permitted.

The warning, issued by Teignbridge District Council, follows an increase in the number of people collecting shellfish and concerns that groups of people are harvesting for onward sale into the wider food chain which could cause serious illness.

Environmental health also undertakes monthly tests on the water and shellfish to ensure its safety and where results are unsatisfactory, commercial fishing must be suspended.

But illegally sold shellfish may not be subject to such checks and so can put people's health at risk from a range of infections such as sickness and diarrhoea, respiratory paralysis, kidney failure, amnesia and even death.

Cllr Alistair Dewhirst Teignbridge's Portfolio Holder for Environmental Health who joined agency staff on their recent inspection with local councillor David Cox warned that anyone collecting shellfish in commercial volumes, or from commercial fished areas could be prosecuted.

He said: "It is really important visitors and residents realise that they must only collect a small amount of shellfish each day and to collect only from parts of the rivers where it is permitted.

"If not properly treated the shellfish can cause serious illness and that is one of the reasons why our officers have been increasing their presence on the rivers and clamping down on those who are breaking the rules.

"We are also concerned about the environmental impact of large scale shellfish collection on the long term sustainability of the estuary for seabirds and wildlife."

Local councillors joined environmental health officers, police and officers from other agencies on a recent inspection of the Rivers Teign and Exe to warn of the health risks of shellfish collection and the importance of sticking to the areas where this is permitted.

Over recent months environmental health officers have been handing out leaflets showing where collections are allowed and warning of the risks of dangerous bacteria and toxins that can be found in shellfish, and they've also worked with local fishermen and parish councillors in an effort to combat the problem.

"There is concern that those collecting shellfish could supply it to the wider food chain, through markets, businesses or to others in their own communities," said Teignbridge District Council's environmental health officer Gavin Fearby.

"Many people do not realise that most shellfish from UK waters require purification in clean sea water to reduce bacterial loading to make the shellfish safer to eat."

Under rights dating back to the Magna Carta, individuals are allowed to collect personal amounts of shellfish per day for their own consumption from designated parts of the shoreline.

However, increasingly reports are being received of people from around the country arriving in groups to harvest shellfish, often from commercial fishing areas.