PARIS (Reuters) - France's would-be president, Nicolas Sarkozy, says children who do not eat pork - the case for many of the country's large Jewish and Muslim minorities - should order a double portion of chips when their school canteen puts ham on the menu.

Sarkozy, trailing rival Alain Juppe in opinion polls as they campaign for conservative party backing in the presidential election six months from now, has sought to present himself as the voice of a silent majority in a formally secular country where the majority are nonetheless of Catholic origin.

Two weeks from a primary election organised by his party, Les Republicains (The Republicans), the man who was president from 2007 to 2012 held a political meeting overnight in his conservative fiefdom of Neuilly, west of Paris.

"If a little guy's family does not eat pork and the menu at the (school) canteen is a slice of ham and chips, well, he skips the ham and eats a double helping of chips. In a republic, it's the same rule and the same menu for everyone," he said.

France, with a total population of more than 65 million, is home to Europe's largest Jewish and Muslim communities.

After attacks claimed by Islamist militants that killed more than 230 people in the past 18 months, security and religious-based tensions are firmly in focus before the election, which will be held in two rounds next April and May.

Opinion polls suggest Sarkozy's main centre-right rival, Juppe, a former prime minister, is favoured both to win the conservative party candidacy and is best-placed to defeat Marine Le Pen, leader of the far-right National Front party, in a possible runoff .

The 'let them eat chips' suggestion is reminiscent of one often - and probably wrongly - attributed to Marie-Antoinette, beheaded wife of King Louis XVI, who in urban legend is reported to have said of bread shortages for the poor: "Let them eat cake".