WARNING: This article contains graphic footage and images that some viewers may find distressing.
Hidden cameras have captured "horrific" abuse of animals in a halal slaughterhouse.
Under the halal code, animals are supposed to be killed quickly with a single sweep of a surgically-sharp knife, should not see the knife or witness the death of other animals.
Footage, courtesy of Animal Aid, was taken inside the slaughterhouse and shows the animals in distress:
UK law states they should also be stunned and left for 20 seconds until they are unconscious before they are slaughtered.
But footage, filmed on a spycam inside the Bowood Lamb abattoir in Thirsk, North Yorkshire, appears to show these rules being broken.
Animals can apparently be seen having their throats hacked and sawed by a worker wearing the traditional Muslim kufi skullcap and muttering the words Allahu Akbar (God is great). In one instance, it took five attempts to sever blood vessels.
The footage is also said to show:
Sheep being kicked in the face and head, lifted by their ears, fleeces or legs, and hurled into solid structures.
A worker standing on the neck of a conscious sheep and bouncing up and down.
Staff erupting into laughter over a sheep bleeding to death with spectacles drawn around her eyes in green paint.
Staff taunting and frightening animals by waving knives, smacking them on the head and shouting at them.
A worker holding a sheep by the throat and pulling back his fist as if to deliver a punch.
The law requires abattoirs to stun animals before slaughter to prevent unnecessary suffering, but there are exemptions for Jewish and Muslim producers.
Four slaughtermen have since had their operating licences suspended following the Animal Aid investigation over three days last December.
The Food Standards Agency (FSA) has now launched an investigation saying there was "no excuse for treating animals in the way shown on the video" and adding that prosecutions could follow.
Kate Fowler, head of campaigns at Animal Aid, said the scenes were "inexcusable".
She spoke to ITV News Calendar about the abuse:
The group is calling for independently monitored CCTV cameras to be compulsory at slaughterhouses.
A petition demanding an outright ban on slaughtering animals without stunning them first has attracted more than 100,000 backers.
But the Government insisted last week it still had "no intention" of outlawing religious slaughter.
Asked about the allegations William Woodward, one of the abattoir's directors, said: "We have no comment to make."
The Muslim Council of Britain said it was appalled at reports of animal mistreatment at an abattoir purportedly following the principles of halal methods of slaughter.
A spokesman said: "Animal cruelty is wrong and criminal wherever it may occur. That it is being carried out in halal slaughter makes it even more incredulous. Animal welfare should be observed by all slaughterhouses."