Ukip has reversed its policy on shechita by backing a ban on non-stun slaughter of animals.
The party is the first to support animal rights groups demanding an end to the practice in kosher and halal abattoirs.
A statement on the Ukip website said: "Animal and veterinary science has long concluded that cutting the throats of animals whilst they are fully conscious can cause significant distress and pain.
"We see no reason why religious groups should not take into account the concerns of animal welfare when carrying out slaughter.
"We find the government response to this issue is weak, lazy and bordering on spineless. It says it would ‘prefer’ animals to be stunned before slaughter but that it must ‘respect the rights of Jewish and Muslim communities to eat meat in accordance with their beliefs’.
"It's 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.”
This comes after Ukip leader Nigel Farage appeared to promise to safeguard shechita.
Speaking at a JC-organised event in 2013, he told the audience: “Even if 71 per cent of Ukip supporters are not comfortable with religious slaughter — perhaps because they come from a different background and it’s not their thing — that’s different to saying to your community ‘you can’t do it’.”
Shimon Cohen, the campaign director of Shechita UK, said: “Citing weak, agenda-led science, Ukip has become the first major political party in the UK to call for a ban on religious slaughter.
"This latest move is opportunistic and a disappointing shift from Ukip's previous position, when both Mr Farage and Stuart Agnew publicly advocated their support for shechita.
“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.”
Speaking in a personal capacity as a farmer, Ukip treasurer Andrew Reid, who is Jewish, backed the policy.
The senior lawyer said: “The argument is very simple. We are backing a ban on non-stun slaughter, not a ban on religious slaughter.
“We are not saying ‘don’t have ritual slaughter’. We are defending ritual slaughter if the animal is stunned first.
“We’re not banning imports of kosher meat, we are just saying, no stunning.
“We have modern standards today, modern developments. There’s a lot in the bible that we wouldn’t do today.
“I don’t consider it antisemitic – this is just looking for a better way of doing it.”
Mr Reid, who owns the Belmont Children’s Farm in Mill Hill, north-west London, added: “If electricity had existed 2,000 years ago, would [religious authorities] have allowed stunning? Who is to say, I can’t say, neither can you or anyone.
“This is about animal welfare. If there is a less cruel way of slaughter, it should come about in my view.
“As a farmer, I would prefer that my animals were slaughtered in the least cruel way.
“I say to people; ‘if you were an animal, which way would you prefer?’”