Shadow environment secretary Mary Creagh challenged the environment secretary Owen Paterson in the House of Commons by claiming the government knew the name of the meat supplier used by Sodexo.
"Will you now name that company, so the rest of the public sector can check their supplies?" said Creagh.
Referring to the scandal as a possible criminal case, Paterson explained that the company would not be revealed, due to the ongoing investigation.
He claimed they had to be careful with what information could be revealed "in case the investigations are impinged upon".
Creagh found the answer "quite extraordinary" and said: "I think the secretary of state has a duty to tell the public what he knows, and in every other case where supermarkets and other suppliers have found adulterated meat products, their suppliers have been told."
Paterson stated that Sodexo had made it "absolutely clear" which products were affected and explained: "This is a criminal conspiracy which covers 23 countries and it does not help the police to arrive at prosecutions if information is revealed."