They says that while some free-range pigs spend their lives outdoors, others are born outside but then spend the most of their life in finishing buildings. It's a strongly held view by the like of Compassion in World Farming and RSPCA, says the NPA.

Government has insisted there is no need for more rules as pig welfare laws are already tighter here than in Europe as a whole.

BPEX has acknowledged the current labelling system does need improvement and says it is hoping to agree standards across the industry.