Le Pen made her claim at the weekend when she said the meat distributed in France's most populous region, which includes the capital, is "exclusively" halal.
She added that "all the abattoirs in the Ile-de-France sell halal meat, without exception."
Halal means lawful in Arabic and can be used to describe meat that has been prepared in accordance with Islamic law.
Le Pen was repeating claims made in a TV documentary in which François Hallepée, the head of Ile-de-France cattle breeders, said all abattoirs in the region were slaughtering according to Muslim ritual.
President Sarkozy made an unscheduled early morning visit to the Rungis food market outside Paris on Tuesday morning where he said Le Pen's claims were "groundless."
"We eat 200,000 tonnes of meat every year in the Ile-de-France and only 2.5 percent is halal," he said.
The agriculture minister also criticised Le Pen's remarks, describing them as "false."
The Rungis market in Paris' southern suburbs is a popular campaign stop for presidential candidates. The site covers 232 hectares and 13,000 people work there every day.
The market is said to be the largest food market in the world. It became the hub for French food in 1969 after the famous original market in Les Halles, immortalised in novels such as Emile Zola's "The Belly of Paris", was unable to cope with demand.