It tested frozen beef burgers taken from store shelves and found that more than a third of brands at five supermarkets contained at least a trace of horse.
Iceland was one of the supermarket chains caught up in the crisis when the Irish Food Standards Agency said some Iceland burgers contained horse DNA. Their products subsequently passed the British tests - which only show positive at more than 1 percent horse DNA trace.
The FSA has said members of the public would be asked if they found low levels - or "trace contamination" - of horse and other species in beef products acceptable.
On Wednesday, the FSA said members of the public were to be asked if they find low levels - or "trace contamination" - of horse and other species in beef products acceptable.
She said trace contamination with other animals - including pig and horse - could take place at abattoirs and processing plants dealing with more than one species "even with thorough cleaning and good hygiene practice".
Adding another food source (horse meat) that is so challenging and impossible to trace is NOT what our USDA needs or the taxpayers need in this country.