The National Pig Association has written an open letter to retailers urging them to support British pig producers as rising feed prices threaten to send them back into the red.

Feed costs have risen 30% recently and over the past month some producers have lost £2 a pig, NPA chairman Stewart Houston claimed in the letter. He also accused retail buyers of putting pork processors under increasing pressure on price, despite the fact ­retail sales volumes remain buoyant.

The letter will be published in trade press this week and follows a number of private letters already sent out to retailers by the NPA in recent few weeks.

"I trust I can count on a positive response from retailers and processors alike," said Houston, reminding retailers of the ­crisis faced by farmers in 2007 and 2008 when on-farm input costs soared and the industry "teetered on the brink of collapse".