Farming leaders have called for immediate action by supermarkets to improve their sourcing and labelling of food in the wake of the horse meat burger scandal.

After burgers sold by Tesco, Aldi, Lidl and Iceland were discovered to have contained horse meat, the National Farmers Union (NFU) warned that consumer confidence in the food industry had been “severely undermined”.

NFU president Peter Kendall said the integrity of UK-produced meat was being compromised by the use of cheaper imports which did not meet the same stringent monitoring systems.

He said retailers must take immediate action to address the integrity of their suppliers and ensure that UK products are easily distinguishable and clearly labelled, so customers can make a conscious decision on the food they buy.

The farming body’s comments come after Tesco took out full-page adverts in a number of newspapers apologising for selling beefburgers containing horse meat. Aldi, Lidl and Iceland also withdrew burgers from sale after they were found to contain horse meat. Sainsbury’s, Asda and the Co-op later withdrew some frozen products but stressed that the move was “purely precautionary” and they had not been found to be selling contaminated food.

Ten million burgers have been taken off supermarket shelves across Ireland and the UK as a result of the scandal.

The ABP Food Group, one of Europe’s biggest suppliers and processors, has stopped work at its Silvercrest Foods plant in Co Monaghan, Ireland, after new tests this week revealed contamination in frozen burgers.

Tests had already shown that Silvercrest Foods and another of the company’s subsidiaries, Dalepak Hambleton in Yorkshire, supplied beefburgers with traces of equine DNA to supermarkets, including one product classed as 29% horse.