Environment Secretary Owen Paterson is to hold a horse meat summit with the Food Standards Agency (FSA) and retailers after it emerged Findus beef lasagnes may have been contaminated since August.
The frozen food company reiterated its apology as the FSA ordered firms to carry out tests on all processed beef foods.
Findus UK confirmed it carried out a full product recall on Monday, two days before DNA tests found some of its lasagnes contained up to 100% horse meat.
The Trading Standards Institute said the discovery of such high levels of horse meat suggested “deliberate fraudulent activity”.
Prime Minister David Cameron said it was a “very shocking story, it’s completely unacceptable” as Scotland Yard said officers had met with the FSA over the scandal.
The force added there is no official police investigation.
And last night discount chain Aldi said tests on its Today’s Special frozen beef lasagne and Today’s Special frozen spaghetti bolognese, which are produced by the same French supplier, Comigel, were found to contain between 30% and 100% horse meat.
Politicians and food safety experts played down the risk to human health, with Mr Cameron, speaking in Brussels, saying it was not about food safety but accurate food labelling and the industry would have to work hard to restore confidence.
“People will be very angry to find out they have been eating horse when they thought they were eating beef,” he said.
Mr Paterson will meet with heads of food retailers and suppliers today at the Department for Environment, Food and Rural Affairs in London, a spokesman said.
The environment secretary said he had “great confidence” in the British food industry but urged consumers to return the affected lasagnes to retailers.
“It is wholly improper the public are presented with a product marked beef when it contains a significant amount of horse,” Mr Paterson said.
Asked whether he would eat the recalled Findus lasagnes, he replied: “Personally I would yes, because what we have in these cases and the FSA has been quite clear is shocking cases of mislabelling.
“But there is no material which has so far been divulged which poses any threat to health.”
Labour MP Tom Watson published a letter on his website which he claimed was sent by Findus to retailers on Monday, warning that a supplier based in France had told it there may be problems with raw materials delivered since August 1 last year.
In it, the firm claimed raw materials delivered to a French contractor since August 1 were “likely to be non-conform and consequently, the labelling on finished products is incorrect”.
The letter added: “The supplier has asked us to withdraw the raw material batches.”
Findus was asked to respond to the claim but has yet to do so.
A company spokesman said its priority was providing quality products customers can trust.
“But we know many people have been concerned by the news this week tests have shown some of our Findus beef lasagne has been found to contain horse meat,” he said.
“We understand those concerns. We are sorry we have let people down.”
The spokesman added the firm “do not believe this is a food safety issue” but anyone who had bought 320g, 360g or 500g Findus beef lasagne packs could call its customer care line on 0800 132584 for advice and a refund.
The frozen food firm, which has its headquarters in London, tested 18 of its beef lasagne products, made by French food supplier Comigel, and found 11 contained in the range of 60% to 100% horse meat, the FSA said.
Retail giant Tesco has also withdrawn a range of ready meals produced by Comigel over fears they contained contaminated meat.