The film, which Animal Aid says was recorded on a number of secretly installed cameras over a period of four days at Elmkirk Ltd (Cheale Meats), an Essex-based, family-run slaughterhouse – shows three different workers stubbing their cigarettes out on the faces of pigs, while one of the men landed a violent punch on the face of a pig who was walking by.

Animal Aid says that in addition, three seriously injured pigs were forced to crawl from the lairage, through the race and into the stun pen.

Animal Aid said it also filmed bad practice in the stunning process causing suffering to the pigs and it says there was also incorrect use of electric goads.

Animal Aid said that Cheale Meats is the ninth UK slaughterhouse to be secretly filmed by them in the past two-and-a-half years.

Animal Aid added that it sent the Cheale Meats evidence to the Food Standards Agency (FSA). It says it recevied a reply saying that: "Defra is not prepared to commence prosecution proceedings where the initial allegation is based on CCTV footage gained without the consent of the relevant Food Business Operator."

Kate Fowler, Head of Campaigns at Animal Aid says: "Since we first began investigating English slaughterhouses, we have been pressing everyone involved – regulators, industry bodies and the government – to act decisively to end the cruelty.

"At first, they appeared contrite and promised action but now their words ring hollow.

"If Defra won’t prosecute these flagrant breaches of the law; if the vets can’t or won’t act to stop the cruelties; and if the slaughterhouse owners look the other way, who is there to stop animals from being abused at the most vulnerable time of their lives? It seems that all involved are content to keep quiet and to allow these cruelties to continue. So much for the UK having the best welfare standards in the world!"

A statement from the solicitor for Cheale Meats, Jamie Foster, a Partner at Clarke Willmott LLP, said: "I am currently reviewing and taking instructions from my clients in relation to video footage provided by Animal Aid. Given the source of this material, Elmkirk would not accept that all or any of the activities shown on this video relate to their premises.

"Elmkirk Ltd have had CCTV installed for a decade. I am therefore surprised that Animal Aid felt it necessary to target our client's premises as we understood that the stated purpose of their activities was to encourage abattoirs in this Country to install CCTV.

"Clearly any footage which relates to our clients premises has been obtained unlawfully. I have been involved in cases previously where such evidence has been ruled to be inadmissible or the Prosecution has declined to rely on evidence which has been obtained by burglary or other unlawful means.

"A complaint has been made to Essex Police by our clients in relation to any unlawful entry into our client's premises by an employee of Animal Aid. The outcome of that complaint is awaited."