CIWF said that the conditions were the worst yet teh organisation had seen within the EU.

Compassion's Investigation Unit identified multiple levels of cruelty, neglect and systematic non-compliance. Compassion has advised that this most recent footage is extremely disturbing and harrowing.

A member of the Investigation Unit said: "Never have I seen pigs so dirty, covered in their own excrement and pens so filthy. Some pens were covered in faeces and the pigs had nowhere to escape from it.

"On a separate farm, pigs resorted to biting dead pigs and using them as play-things, as they had nothing else to occupy them."

According to Compassion, not only is this a horrific animal welfare issue, but it also brings to light obvious questions regarding food safety. All the farms visited suffered from fly infestations, with some of the pigs suffering with open wounds. In the third farm we found evidence of fresh tail wounds caused by tail biting and injuries caused by fighting. Many of the pigs were in pain and living in barren and often insanitary conditions.

Compassion's Chief Policy Advisor, Peter Stevenson, has written to the Irish Minister, Simon Coveney. He said: "The conditions we saw on all five farms are deplorable and do not comply with the EU legislation that is meant to protect the welfare of pigs. We urge the Irish authorities to take urgent action to secure compliance by the Irish pig sector with the requirements of EU legislation on the welfare of pigs.

"Many of the pigs in one farm had open wounds and one with a festering wound was resting in the pen’s feed trough. In the fourth and fifth farms we found dead pigs in the ordinary pens."

In addition, Mr Stevenson has written a formal complaint to the Commission. This follows on from complaints on behalf of Compassion in 2009 and 2011. The fact that nothing has been done to improve the welfare of the pigs is astounding. In light of this lack of action, we are urging the British public to buy British pig meat that is labelled as higher welfare and not to support this illegal Irish farming. Recent statistics state that in 2011, the UK was the main market for Irish pig meat: taking over 46 per cent of Irish total exports.

Dil Peeling, Compassion's Director of Campaigns, said: "The levels of neglect on all of the farms points to a systemic failure and the barbarity of this situation points to two options: either the government doesn't care or they are incompetent. Either of these is inexcusable.

"In some of the farms there was a 'hospital area' which would be laughable if it weren't so devastating: an emaciated pig left to die, dying pigs lying on top of one another. It is a real-life hell-hole."

CIWF's Irish pig investigation footage can be found by clicking here.