The number of animals killed without being stunned has risen sharply under a government exemption for Muslims and Jews from humane slaughter rules.
Almost a quarter of lambs had their throats cut without first being made insensible to pain, according to Food Standards Agency figures for April to June this year.
This was an increase from 2013 when 15 per cent of lambs were killed without being stunned and 10 per cent in 2011. The change has been attributed to an increase in halal slaughter rather than the Jewish shechita method.
The figures also revealed that almost a fifth of chickens are slaughtered without being stunned or after a stun that is too weak to guarantee that they do not feel pain.
The numbers indicate that, on an annual basis, more than three million lambs are being killed without being stunned and almost 200 million chickens are either not stunned or are ineffectively stunned.
Poultry can take two and a half minutes or more to lose consciousness after their throats are cut and lambs 20 seconds, according to the European Food Safety Authority’s scientific panel on animal health and welfare.
The British Veterinary Association condemned the increase and called on the government to remove the religious exemption from the requirement for all animals to be stunned before they are slaughtered.
Gudrun Ravetz, the association’s president, said: “This huge increase in the number of sheep, goats and poultry that are not stunned or not stunned effectively before slaughter is a grave concern to our profession.
“Millions of individual animals are affected, making this a major animal welfare issue.
“The supply of meat from animals that have not been stunned massively outstrips the demand from the communities for which it is intended and is entering the mainstream market unlabelled.
“In the light of these official figures we reiterate our call for all animals to be stunned before slaughter.
“If slaughter without stunning is still to be permitted, any meat from this source must be clearly labelled and the supply of non-stun products should be matched with demand.”
For meat to be halal, the animal must be alive when its throat is cut and die from loss of blood. Some halal abattoirs pre-stun animals but use methods that are guaranteed not to kill the animal.
Research has suggested that the electric shock used by the halal industry to stun chickens may be too weak to ensure that they feel no pain while being killed.
A spokesman for the Department for Environment, Food and Rural Affairs said: “We are clear that animals must be stunned before slaughter unless they are being slaughtered for religious purposes.
“The law enables people to eat meat killed in accordance with their religious beliefs. There are strict rules to provide the maximum possible protection to animals subject to religious slaughter.”