It claims every safety recommendation has been implemented, and that there is no reason to ban the sale of lamb or other sheep products.

However, the Department of Health accepts that further research is needed into the possibility of BSE contamination.

Government scientists have known for some time that there was a risk that sheep have been contaminated with BSE.

The Spongiform Encephalopathy Advisory Committee set up to study BSE reported in July 1996 that the condition had been experimentally transferred to sheep through feed.

The SEAC scientists also concluded that there was no evidence that BSE had entered the British flock.

'Matter of prudence'

However, they did, as a "matter of prudence", recommend that the brains of sheep aged more than 6 months be removed from the food chain, and that Britain talk through the potential risks with its European Union partners.

In May 1997, SEAC recommended that the spinal cord and the spleen of older sheep also be removed from the food chain.

The committee also recommended a three-point strategy for dealing with the related sheep disease scrapie.

This included a compulsory slaughter and compensation scheme for animals identified as carrying the disease, an abattoir survey of 3,000 sheep and a postal survey about the incidence of scrapie sent to 5,000 farmers.

Government response

The government responded to SEAC's recommendations by banning sheep and goats heads from the animal and human food chain in September 1996.

A ban on the use of spinal cords of sheep aged more than 12 months, and the spleens of all sheep followed in January 1998. This was introduced unilaterally by the UK Government after talks stalled with the EU.

Despite the government's action, a Ministry of Agriculture spokesman refused to give a guarantee that sheep meat is safe.

She said: "We acknowledge the theoretical risk and we have taken precautionary measures to ban specific risk material as advised by SEAC.

"The committee has not recommended that further measures are necessary."

CJD link

BSE was first isolated in cattle

The full impact on human health of BSE is not fully understood, but there is strong scientific evidence that the condition is linked to fatal human neurological condition Creutzfeldt-Jakob Disease (CJD).

The UK Government announced in 1996 that a new strain of CJD had emerged, and that it was probably contracted by eating BSE infected meat.

At present there are 26 confirmed cases and one probable case of the new variant of CJD in the UK known to the CJD surveillance unit.

The degree to which infected sheep may contribute to the human toll is unknown.

The 1988 ban on feeding meat and bonemeal to cattle to combat the risk of BSE was extended to sheep as well.

However it is known that cattle farmers flouted the ban, and the likelihood is that sheep farmers acted similarly.

Experts believe that if sheep are infected with BSE, then the majority of the population will already have been exposed to the risk.

Young children alert

The Consumers' Association has advised that parents should not introduce lamb into the diets of young children as a precaution.

However it is likely that if any risk exists, it is likely to come from mature ewes whose tissue would have accumulated the BSE infection over several years.

Most lambs are slaughtered in the first 12 months of life before they have had time to become particularly infectious.

The first cases of Bovine Spongiform Encephalopathy (BSE) were seen in cattle at the end of 1984.

BSE, dubbed mad cow disease by the popular press, is a neurological disease causing brain damage, disorientation and eventually death.

It produces fluid-filled cavities - vacuoles - in the brain cells, giving them a spongy appearance.

Initially it was thought that BSE was a variant form of scrapie - a similar brain disorder - that had jumped from sheep to young cattle, who were fed on the ground-up remains of slaughtered animals including sheep.

However there is no proof that scrapie can jump to another species.

Sceptics say the sheep disease has been around for at least 200 years and sheep products have been included in cattle feed for several decades.