The RSPCA has begun an investigation after footage of pigs apparently being tortured and beaten to death on a Norfolk farm was uncovered from an undercover investigation.

Animal rights group, Animal Equality, has produced video footage of animals being kicked, slapped and beaten with iron bars and gate rods, and workers scraping a knife across the backs of pigs to force them to move.

They sent an undercover investigator to work at Harling Farm, near Thetford, for two months last summer and say they have gathered more than 200 hours of harrowing footage and 300 photographs.

One section of the footage shows a worker repeatedly beating a pig on the face with a plastic rod.

The same worker is seen using an iron bar to beat a pig to death, raining down repeated strikes until the animal is left twitching on the concrete.

Michael Brown, who runs the farm, told the EDP today that he was not aware of any cruelty on the farm until RSPCA investigators turned up on Friday.

He said: 'We are horrified to learn what has allegedly happened and have dealt with the staff involved appropriately.

'We are co-operating fully with all investigations and are pleased that the RSPCA has visited and approved all our practices at the farm.

'We take animal welfare extremely seriously and place it at the heart of everything we do here.'

An RSPCA spokesman said: 'The footage is some of the most shocking we have ever received and we are taking this most seriously.'

Animal Equality said the investigation 'marks the beginning of an intensive campaign to reveal the true face of animal farming in Britain, and provides a stark contrast to the pig industry's celebrity-endorsed 'Love Pork' marketing campaign.'

The farm had been approved by the Red Tractor food quality assurance scheme which aims to ensure responsible farming methods.

David Clarke, chief executive of Assured Food Standards, which runs the Red Tractor scheme, told The Sunday Times, that Harling Farm had been suspended from the programme pending the findings of an inspection.

He said: 'If the allegations are proven they are completely unacceptable and all necessary action will be taken, including exclusion from the scheme.

'In such a case we would also support the prosecution of those responsible.

'We believe our inspections are rigorous and effective and we are exploring why these problems weren't picked up.'