The RSPCA and the British Veterinary Association (BVA) have joined forces to demand the end to a legal exemption permitting animals to be slaughtered without pre-stunning.
The organisations said slaughter without the welfare measure was causing unnecessary pain and suffering to as many as 120 million animals a year.
In an open letter to Environment Secretary Michael Gove, the BVA and the RSPCA also urged for the Government to improve transparency on the issue by releasing the comprehensive 2018 slaughter survey results - originally due for release autumn 2018.
Until a full ban is in place, the RSPCA and BVA are calling for the following measures to be taken:
The letter follows a recent, high-profile decision to ban the slaughter of animals without prior stunning in the Flanders region of Belgium.
Several other European countries, including Iceland, Sweden, Switzerland and Denmark also have a full ban on non-stun slaughter.
The most up-to-date Food Standards Agency (FSA) figures show that in the UK between October 2017 to September 2018, over 120 million animals were slaughtered without pre-stunning.
The figure includes:
RSPCA chief executive, Chris Sherwood said: "We’re opposed to non-stun slaughter and we’re calling for an end to the practice as it seriously compromises animal welfare.
“Our concern does not relate to the expression of religious belief but the welfare of animals.
Until there is a change in the law to end non-stun slaughter, there are several measures the UK Government could introduce to reduce the suffering involved in this practice.
"For example, by ensuring trade deals with other countries do not include non-stun meat or live animals for non-stun slaughter, clear labelling should be adopted to enable consumers to make an informed choice about the meat they buy and how it was slaughtered."
BVA president Simon Doherty added: “The UK Government has repeatedly stated it would prefer to see all animals stunned before slaughter but has taken no action to address this critical welfare issue that affects millions of animals every year.
"It is doubly disappointing that data that would have provided a valuable benchmark for levels of non-stun slaughter in the UK has yet to see the light of day despite assurances throughout last year that it would soon be made public.
Michael Gove has made clear that he wants to maintain and build on the UK’s reputation as a global leader on animal welfare; banning non-stun slaughter is a surefire way of showing he will deliver on this commitment.
“If slaughter without stunning continues to be permitted in the UK, then meat and fish from this source must be clearly labelled, to help customers make informed choices about the food that they buy and eat.”