Sir: Four member states are breaking the law by not complying fully with the partial sow stall ban that became law through the EU in January 2013.

Should Belgium, Cyprus, Greece and France fail to comply with EU law within two months, they may be referred to the EU Court of Justice. A number of UK retailers are known to source their pork from these non-compliant countries.

Retailers will no doubt claim that they only use pork from farms that are compliant. Yet how rigorously is this policed? It must surely be easier to guarantee compliance where the whole of a country’s pig production is proven to be compliant rather than just certain farms.

Furthermore it could be argued that by purchasing pork from non-compliant countries any company - processor or retailer - is complicit in supporting illegal production.

Richard Longthorp OBE, chairman, National Pig Association