Environment Secretary Owen Paterson says retailers hold the “ultimate responsibility” for making sure that horsemeat is not in their products.
After attending an emergency meeting with bosses from leading supermarkets and the Food Standards Agency (FSA) to discuss the scandal, Mr Paterson said retailers would have to start doing their own testing.
“Ultimate responsibility for the integrity of what is sold on their label has to lie with the retailer”, Mr Paterson said.
Mr Paterson said that during this morning’s talks the supermarkets agreed to work with the FSA to report their test results on a quarterly basis.
Mr Paterson said investigations would find whether “either gross incompetence or criminal acts” were at fault.
He warned of a possible “international criminal conspiracy” being behind the scandal.
“If there’s a criminal act we will work with the authorities wherever they are to ensure the appropriate measures are taken,” he added.
“It’s a straight fraud. If a product says it’s beef and you’re actually buying horse, that is a fraud.
“It is in the interests of everyone to get this resolved as rapidly as possible.”
Bosses from leading supermarkets including Tesco, Sainsbury’s, Asda and Morrisons attended the meeting at the Department for Environment, Food and Rural Affairs (Defra) in London.
The talks come as frozen food company Findus UK reiterated its apology after tests found up to 100 per horse meat in some of its beef lasagnes.
Supermarket chain Aldi confirmed that two of its ready meal ranges produced by Comigel, the French supplier also used by Findus, were found to contain between 30 and 100 per cent horse meat.
And on Friday night, the scandal became a police matter as Scotland Yard announced they had met representatives from the FSA.
Prime Minister David Cameron said it was “shocking” and “completely unacceptable”, as the FSA ordered firms to carry out tests on all processed beef foods.
A company spokesman said its priority was providing quality products customers can trust.
“But we know that many people have been concerned by the news this week that tests have shown that some of our Findus Beef Lasagne has been found to contain horse meat,” he said.
“We understand those concerns, we are sorry that we have let people down.”
Morrisons chief executive Dalton Philips told Channel 4 News it was possible that the supermarket chain would pull all Findus products off its shelves after admitted that he cold not be “one hundred percent” sure about the contents of branded meat products in his stores.
He said: “We’re going to talk with Findus and understand what happened. If we don’t feel that we can get to the bottom of this we’ll be taking strong action.
Mr Philips blamed the current crisis on the complexity of the food chain and the pressure on manufacturers to costs, with horsemeat half the price of beef.
He added: “I can see how it could get introduced by some fraudulent or unscrupulous behaviour.”