Labour has pinned the blame for the discovery of traces of horse DNA in Tesco's beef burgers on the coalition's drive to reduce regulation.
The comments come as Britain faces the mass trauma of possibly having inadvertently eaten horse - and Jews and Muslims learned they may well have eaten pork in supermarket beef products.
"Consumers will be rightly concerned by this news. People should be able to go into the supermarket and be confident that what that they are buying for their families is legal and safe," shadow environment food and rural affairs secretary Mary Creagh said.
"There are serious questions for the government to answer about what happened and why it wasn't detected by British food safety authorities.
"This is a wake up call for the government and retailers that rolling back regulation that protects our food serves no-one and is against consumer interest."
Labour MP and rural affairs committee member Barry Gardiner said there should be an inquiry into the affair.
"You expect what is on the label is what you get, and a beef burger is not a horse burger. Most people would be horrified to find they have been eating horse," he said.
Tests by the Food Safety Authority of Ireland found low levels of horse DNA in beef products sold in Tesco, Lidl, Aldi, Iceland and Dunnes Stores.
Horse meat apparently accounted for 29% of Tesco's Everyday Value Beef Burgers.
Over a third of products tested in Ireland were found to have horse DNA and a majority (85%) contained pork.
The Food Standards Agency (FSA) is meeting today to discuss the problem.