Changes to the way shellfish are tested are being urged following the latest closure of the cockle beds between Gower and Carmarthenshire.
The cockle beds will not be open again this month
It is the first time the whole of the Burry Inlet has been off limits to gatherers since August after cockles on both shores tested positive for Diuretic Shellfish Poisoning or DSP.
The announcement on Thursday has left 55 licensed gatherers out of work and they will not be able to pick cockles until next month at the earliest.
It is the latest in a continuing saga that has hit the cockle industry in Wales.
Rory Parsons who runs a processing plant in Burry Port says the DSP test used in Britain is unreliable and should be replaced.
It is a blow for the cockle gatherers but we cannot takes any chances when it comes to protecting public health
Carmarthenshire Council's Phil Davies
"This is a very sad and frightening day for the whole of the cockle industry," said Mr Parsons.
"This is the first occasion since zoning was introduced for the Burry Estuary last August that it has been totally closed - prior to zoning the entire fishery was closed continually for 14 months."
Samples of cockles are collected by officers from Swansea and Carmarthenshire councils on behalf of the Food Standards Agency (FSA) and sent to the Centre for Environment, Fisheries and Aqua-culture Science in Weymouth.
"This test uses three suckling baby mice, which are all injected with a concentrated cocktail of cockles and other chemicals," added Mr Parsons.
"The equivalent oral test for a human would require a human to eat 1.33 times their own body weight of cockles in one sitting alone.
"The FSA refuses to use other tests that are more accurate and which are the accepted methods for other countries such as Holland, Ireland and New Zealand.
"These countries have abandoned and will not use the mouse test because it is well known by them to be unreliable.
"Cockles from these other countries are being imported into the UK."
Carmarthenshire Council's head of public protection Phil Davies said there will need to be two consecutive negative tests before the beds can be re-opened.
He said contaminated cockles can lead to nausea, vomiting, abdominal pain, diarrhoea and chills.
"Tests will now be carried out weekly," he said.
"It is a blow for the cockle gatherers but we cannot takes any chances when it comes to protecting public health."
The FSA spokesman said the European Union (EU) law requires testing of cockle beds for a number of toxins, one of which can cause DSP.
"This toxin could be harmful to people and that may not be apparent for many years.
"We've carefully considered the tests and have no doubts about the methodology used by our laboratories.'
The FSA says it has tried to reduce the impact of the closure of cockle beds on fishermen, while still protecting public health.
It is doing this by dividing up fishing areas into zones and lifting the ban on those zones where further tests proved negative.