The number of animals killed without pre-stunning has risen sharply, according to analysis by the British Veterinary Association (BVA) of the latest survey released by the Food Standards Agency (FSA).
The BVA said that slaughter without stunning "unnecessarily compromises" the welfare of animals at the time of death.
However, almost a quarter (24.4%) of sheep and goats slaughtered between April and June this year had their throats cut without first being made insensible to pain.
There has also been an increase from 15% in 2013, when the EU and UK-adopted legislation allowing an exemption for animals that are slaughtered for religious purposes came into force.
The number of chickens being slaughtered without pre-stunning has soared from 3% in 2013 to 18.5% in 2017, the FSA figures also revealed.
The BVA has labelled the figures a "grave concern" to the veterinary profession, and called for all livestock to be stunned before slaughter.
If this is not possible, the body said to "clearly label" all meat sourced from non-stun slaughter, and for the supply of non-stun products to be matched with demand.
British Veterinary Association President Gudrun Ravetz 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.”
Welfare at slaughter is one of the UK’s most pressing health and welfare concerns for vets, according to BVA’s latest member survey.
The leading body for vets has campaigned for the re-introduction of law that guarantees all animals are stunned before slaughter on the grounds of animal welfare.
Yet while legislation exists to permit slaughter without pre-stunning, BVA is calling for any meat or fish from this source to be clearly labelled to enable customers to understand the choice they are making when purchasing such products.