By Nick Lester, Parliamentary Correspondent
David Cameron side-stepped a question from Exeter MP Ben Bradshaw over whether he had eaten processed meat since the food scandal erupted.
The former Environment Minister tackled the Prime Minister in the Commons over the growing horse meat controversy.
But Mr Cameron only said he followed the advice of the Food Standards Agency, which reported there were no unsafe products on supermarket shelves.
It came as the PM defended the Government's response to the crisis, saying it was insisting on "meaningful" tests of products by retailers and suppliers.
He vowed that anyone involved in passing off horse meat as beef would face the full force of the law after two British plants were raided and shut down.
"If there has been criminal activity there should be the full intervention of the law," he said.
Quizzing the PM at Westminster, Mr Bradshaw said: "Is the Prime Minister still eating processed beef?"
In response, Mr Cameron said: "I am following very carefully what the Food Standards Agency says, and what the Food Standards Agency says is that there is nothing unsafe on our shelves."
The PM said it was 'appalling' and "completely unacceptable" that consumers were buying beef products that turned out to contain horse meat.
He said many of the current issues had come to light due to tougher tests that had been ordered by ministers, and pledged that in future results would be made public.
"We have also asked for meaningful tests from retailers and producers and they will be published in full," he added.
Faced with a barrage of questions from MPs, Mr Cameron said: "Retailers I think do bear a real responsibility here.
"At the end of the day, it is they who are putting products on their shelves and have got to say that they are really clear about where that meat came from, what it was, who it was supplied by. It is up to them to check that and I think that is vitally important."
Downing Street insist the Government has "got a grip" on the horse meat issue.
The Prime Minister's official spokesman said: "The Government, working with the FSA, is doing the right thing."
Shadow Environment Secretary Mary Creagh has called for Europe-wide testing of meat products, raising concerns that horse meat sometimes contained the painkiller bute, and could have entered the food chain.