The FSA has asked retailers to test beef products for the presence of more than 1% of horsemeat, with anything above that figure considered to be a sign of adulteration.
Subsequent rounds of testing revealed adulteration in some products sold by Asda, Sodexo - which supplies food to schools, care homes and the armed forces - and the Whitbread Group.
MPs rejected a motion calling for the government to ensure that the police and fraud specialists investigate criminal networks involved in horsemeat adulteration and speed up the FSA tests to restore consumer confidence.
The 1938 Food, Drug and Cosmetic Act bans the adulteration of food by any agent intended to dupe the consumer into thinking the product is superior in quality or more nutritious than it actually is.