The National Front’s Le Pen, trailing both Sarkozy and Socialist frontrunner François Hollande ahead of the April 22 vote, made the claim at a rally on Saturday and pledged
to file a legal complaint for "misrepresentation of products".
Campaigning on Tuesday in Rungis, home of the main wholesale food market serving the Paris metropolitan area, Sarkozy accused Le Pen of creating an artificial controversy and getting her facts wrong.
"There is no controversy here. Every year we consume 200,000 tonnes of meat in the Paris region and 2.5 per cent of it is kosher or halal," Sarkozy said.
Le Pen, whose party plays on fears of growing Muslim influence, cited a recent public television documentary that said all abattoirs in the greater Paris region use halal methods but do not always label the meat as such.
"It turns out that all the meat distributed in Ile de France is, unbeknownst to the consumer, exclusively halal meat," she said on Saturday. "This is a real deception, the government has been aware of this for months."
On Tuesday she clarified her comments to say that all meat distributed in the region could be suspected of being halal, as without a label "neither I nor you know which is halal and which is not".
Halal meat is slaughtered according to Islamic rules that, among other requirements, ban the practice of stunning animals before they are killed.
Some animal welfare campaigners say this is more cruel than standard European practices.
"Widespread animal suffering, in violation of French and European law, is not trivial," she said on France Inter radio in response to Sarkozy.
"The fact that a majority of French people are being misled about what they buy is not a trivial controversy," Le Pen said.