Image copyright Getty Images Image caption Chickens slaughtered according to Islamic practice

It's a passionate conflict - animal welfare campaigners opposing the slaughter practices of religious minorities.

Could it be a topic that persuades undecided voters on polling day?

Always an emotive issue, religious slaughter has become an unexpected political battleground as the general election approaches.

Animal rights campaigners have long called for a ban on halal or shechita slaughter, which amongst other requirements specify slitting an animal's throat quickly with a sharp knife while it is still conscious.

Halal slaughter has been especially targeted by certain groups to attempt to discredit humane halal slaughter methods Halal Authority Board

The British Veterinary Association, the RSPCA, Compassion in World Farming and the National Secular Society all want to see an end to the religious slaughter of animals or to slaughter without pre-stunning.

However, in the run-up to the general election, opposition to those methods of slaughter would also seem to have become dog whistle politics: shorthand for targeting a specific religious minority - Muslims - without saying as much.

UKIP last week said it would ban all slaughter methods that didn't involve pre-stunning - causing controversy amongst British Muslims and Jews, some of whom warned that any such ban would in effect drive those who observe religious dietary laws out of the UK.

For many of the UK's almost three million Muslims, halal slaughter is a strict religious requirement, as is eating kosher for many of the UK's 300,000 Jews.

Rules over stunning

According to the Halal Authority Board, there is a strong strand of religious opinion that livestock should not be stunned before slaughter, but others feel that light stunning is permissible.

Its standards permit both types of slaughter, and dictate a number of requirements regarding animal welfare for both.

"If followed properly, both unstunned and stunned are extremely humane forms of slaughter and the evidence to suggest otherwise is completely wrong," according to its head of certification, Shaykh Tauqir Ishaq.

Image copyright PA Image caption Under the halal code, animals are supposed to be killed quickly with a single sweep of a surgically-sharp knife

"Being cruel to animals is a sin in Islam, and we do not permit any form of cruelty in abattoirs certified by us.

There is a danger that an outright ban on religious slaughter would not improve the welfare of animals at the point of slaughter Neil Parish MP, Associate Parliamentary Group for Animal Welfare

"The discomfort and pain experienced by any animal should be absolutely minimised if not eliminated, and our standards reflect such requirements.

"We have found that all abattoirs we have visited, audited and certified pay great attention to animal welfare from transportation, temporary storage and stunning and slaughtering. Whilst the taking of an animal's life is not a pleasant one, it is permitted in Islam as long as it is for eating and not sport."

The most recent debate over religious slaughter was sparked off by images released by Animal Aid, showing "horrifying yet routine abuse" captured using hidden cameras at a halal abattoir.

One worker was sacked and three others suspended after being filmed breaking the strict rules on slaughtering sheep by hacking and sawing at the animals' throats.

The men at the Bowood Lamb abattoir in Thirsk, North Yorkshire, could be prosecuted.

However, Animal Aid is keen to point out that prior to Bowood, it had filmed undercover in nine other slaughterhouses, all of them practising mainstream "humane" killing with pre-stunning.

In all but one of the nine, the group recorded "appalling and often gratuitous cruelty".

Animal Aid's position is that all slaughter involves suffering, so it promotes an animal-free vegan diet.

British and EU law requires all animals to be stunned prior to being killed, unless the meat is intended for Muslim or Jewish consumers.

Laws not applied

However, Animal Aid said it had discovered a "remarkable weakness in the application of the law", with the regulatory body, the Food Standards Agency, acknowledging to Animal Aid that any slaughterhouse "can practise non-stun slaughter without demonstrating that the meat is destined for religious communities."

The Halal Authority Board said that it was "shocked at the cruel practices that have been filmed and these persons and abattoirs should be held to account".

But it went on to say: "We also feel that halal slaughter has been especially targeted by certain groups to attempt to discredit humane halal slaughter methods."

UKIP is the only British political party so far to promise to ban the killing of animals for meat in the UK without stunning them first.

Halal and Kosher meat:

Halal is Arabic for permissible. Halal food is that which adheres to Islamic law, as defined in the Koran.

The Islamic form of slaughtering animals or poultry, dhabiha, involves killing through a cut to the jugular vein, carotid artery and windpipe.

Animals must be alive and healthy at the time of slaughter and all blood is drained from the carcass. During the process, a Muslim will recite a dedication, know as tasmiya or shahada.

There is debate about elements of halal, such as whether stunning is allowed.

Stunning cannot be used to kill an animal, according to the Halal Food Authority (HFA), a non-profit organisation that monitors adherence to halal principles. But it can be used if the animal survives and is then killed by halal methods.

Kosher food complies with Jewish dietary law (kashrut), again governing what can and cannot be eaten by those practising the faith.

There are similarities in the method of slaughter in that both require use of a surgically sharp knife and specially-trained slaughtermen.

Jewish law strictly forbids the use of stunning and meats are not blessed in the same way.

Unlike for halal, kashrut does not require God's name to be said before every slaughter after an initial blessing.

Kashrut forbids the consumption of certain parts of the carcass, including the sciatic nerve and particular fats.

Halal also forbids consumption of some carcass parts including the testicles and bladder.

Prime Minister David Cameron, who has said he is happy to eat halal meat, has promised to keep exemptions for religious purposes such as halal and Jewish shechita for kosher meat.

However, UKIP said that it was "about time someone stood up for the rights of the silent majority in the ethical treatment of animals instead of bowing down to those who shout the loudest".

In a statement, the party noted: "We respect religious groups to carry out slaughter in the UK according to how they define and read their scriptures.

"What we do not allow, however, is for the rights and demands of groups within those religion to override the UK's compassionate traditions of animal welfare.

"We see no reason why religious groups should not take into account the concerns of animal welfare when carrying out slaughter."

The party's agricultural spokesman, Stuart Agnew, was quoted in the Jewish Chronicle as saying that he had been against the policy change, but had been overruled.

He told the newspaper that the policy was not meant to "target" Jews, but was "aimed elsewhere - it's aimed at others. You've been caught in the crossfire; collateral damage. You know what I mean."

'Opportunistic shift'

Shimon Cohen, the campaign director of Shechita UK, hit back at the party.

He said: "This latest move is opportunistic and a disappointing shift from UKIP's previous position, when both Nigel Farage and Stuart Agnew publicly advocated their support for shechita.

Image copyright PA Image caption An estimated 10% of sheep slaughtered in Britain are not pre-stunned

"UKIP's new assertion that '[mechanical] pre stunning before religious ritual slaughter is fully compatible with all world religions,' is plain nonsense.

"The Jewish community does not permit any of the industrialised mechanical stunning methods used in factory slaughter.

"By joining the campaign to prioritise 'animal welfare' over the rights and beliefs of the UK's faith communities UKIP has returned to the fringes of mainstream politics."

A Westminster Hall debate in November last year on religious methods of animal slaughter cited figures from the all-party group on beef and lamb that suggested about 90% of lambs and 88% of chickens slaughtered under halal were stunned before slaughter.

However, an estimated 3% of cattle, 10% of sheep and goats, and 4% of poultry slaughtered in Britain were not pre-stunned.

Some 114 million animals are killed annually in the UK using the halal method, while a further 2.1 million are killed under the shechita method, with the value of the halal market estimated at between £1bn and £2bn.

Ban 'counter-productive'

Neil Parish MP, the all party group's chairman, said that there "is a danger that an outright ban on religious slaughter would not improve the welfare of animals at the point of slaughter.

"At the moment about 80% of the halal meat produced in this country has been stunned.

"Driving our halal and shechita meat industry abroad to countries without our robust animal welfare standards and our supply chain traceability might result in more animals being slaughtered without stunning."

Image copyright PA Image caption UK slaughterhouses must be completely halal compliant

Louise Ellman, Labour MP for Liverpool Riverside, emphasised the importance of Jewish methods of slaughter and kashrut (Jewish religious dietary laws) to the whole Jewish community.

"It recognises its rights as part of British society as well as enabling individual Jewish people who observe the laws of kashrut to eat meat and poultry. Any interference with their ability to do so would be a gross infringement of civil rights."

She said that the Jewish laws of kashrut were part of a wider concern for animal welfare.

"Shechita is carried out by trained, licensed experts. Animals are killed by a single cut to the throat in a prescribed way from a special surgically sharp knife that is regularly inspected.

"Blood flow to the brain is immediately cut off with consequential inability to feel pain and subsequent rapid death.

"There are too many other rules of kashrut to enumerate here, but it is important to point out that they are all related to enhancing animal welfare."

Mechanical stunning can also have a high failure rate, Mrs Ellman pointed out.

"Many more animals suffer because of inadequate stunning than are killed altogether by shechita.

"The report of the EU Food Safety Authority stated that failure rates for penetrative captive bolt stunning may be as high as 6.6% - 2 million cows.

"It also reported that failure for non-penetrative captive bolt stunning and electric stunning could be as high as 31% - 10 million cows.

"In comparison, the total number of cattle killed by shechita [in the UK] in any one year is 20,000."

The one area where some MPs and lobby groups tend to agree that more should be done is in labelling meat to make clearer to all UK consumers what methods were used in its slaughter, and in ensuring that all abattoirs have CCTV to ensure that the law is complied with.

Clearer labelling would also help Britain's Sikhs, who cannot eat halal or kosher meat.