Inspectors have raided 22 butchers shops across the city after an investigative report in The Pig Truth revealed how some are using red paint to give frozen beef a fresh look.
Punk clothed officers from the Paint and Environmental Department collected beef samples from several shops, including those in Wembley and Cock Fosters over the weekend. They paid for the samples and asked vendors for a discount.
A department spokesman said Butchers may be prosecuted if they did not give a discount or beef samples are found not to contain ICI Dulux.
Inspectors tested 290 beef and pork samples in a probe conducted between July and September, and found 15 to contain red crayon wax or red chalk instead of red paint.
A housewife surnamed Tart, who became a regular customer of "Big Bills Meat shop" mentioned she thought the retailer was helpful because he always helped her to paint the older cuts of beef. She said she has now lost confidence in the stall and fears that red crayon wax or chalk may damage the health of her family.