Docking involves cutting off part of the tail, invariably without anaesthetic.
A report by the European Food Safety Authority and Compassion in World Farming's recent supermarket survey show that 75-80% of British pigs are still tail docked five years after the ban came into force. EU legislation banned the routine tail docking of pigs in 2003. Many British pig farmers ignore the law.
CIWF said tail docking - which scientific research has established to be painful - is carried out to prevent tail biting.
It claims in today's industrial pig farming animals are packed into overcrowded barren pens and are usually kept on slatted or perforated floors without any straw. In natural conditions pigs are highly active spending 75% of their day rooting, foraging and exploring. Such activities are impossible for industrially farmed pigs.
It added that scientific research showed that the right way to prevent tail biting is to keep the pigs in good conditions, not to dock their tails. This argument was accepted by the EU when it banned routine tail docking in 2003.
Peter Stevenson, chief policy adviser at CIWF, said: "I am shocked that many British pig farmers are flouting the law that bans routine tail docking. Despite repeated requests to Defra, they have failed to take effective action to enforce this law - this is why we have today made a Formal Complaint to the European Commission.
"Tail docking props up the factory farming of pigs. If farmers could not tail dock, they would have to provide higher welfare conditions for the pigs - in particular, they would have to give their pigs enough space to prevent overcrowding and straw to enable them to engage in their natural rooting and exploratory behaviours."