An investigation has been launched after workers were secretly filmed violently abusing pigs at a farm owned by one of Britain's biggest producers.

Campaign group Animal Equality released horrific footage of the animals being kicked in the head, jabbed with pitchforks and hit with gates.

Four workers at Fir Tree pig farm in Lincolnshire, have since been sacked and the the video has been passed to the RSPCA and government to investigate.

Following an anonymous tip off, the cameras were placed around the farm and show some employees pictured swearing at the animals, as they joked about the abuse.

One pig appears to look so unwell that it is cannot move.

It is then shifted into the bucket of a tractor, thrown into a pen and squeals in agony as it is hit repeatedly.

Afterwards the pig was said to have been left without veterinary attention for 48 hours, before it was shot.

Farm owners the Godfrey family, along with the company Elsham Linc LTD, have since dismissed the staff members who appeared in the video.

Four workers at Fir Tree pig farm in Lincolnshire, have since been sacked and the footage has been passed to the RSPCA and government to investigate

They told Sky News: 'We are shocked by the actions of those involved as their abhorrent behaviour does not represent our business.

'We are a family run farm where the care and welfare of our pigs is paramount.

'We have been able to identify the four individuals in the film and following an immediate investigation their employment has been terminated.'

Dr Toni Shephard, Animal Equality's UK Director, added: 'While intensive pig farms are inherently pitiless places, the brutality inflicted on these poor pigs is incomprehensible.

'The workers show complete contempt for the animals in their care and seem immune to their suffering, even when the pigs scream in pain. We demand that they be brought to justice.'

Most British pigs are kept locked inside sheds and barns for their entire lives.

Supermarkets including Co-op are Waitrose have pledged to stop sourcing their meat from farms that are not free range in the coming years.

However Dr Shepard goes on to say that the best way to end cruelty to pigs is to cut out meat altogether.

She added: 'Consumers can help end this cruelty by trying the increasing variety of plant-based foods available in shops and restaurants, which are often healthier than meat as well as cruelty-free.'