Marine Le Pen has appeared in court in Lyon, to answer charges of inciting racial hatred, for comparing Muslims praying in the street to the Nazi occupation.
The French National Front (FN) leader made the comments at a rally in Lyon in 2010 when she was fighting for the leadership of the party.
Marine Le Pen’s anti-immigration and anti-EU message is attracting increasing support in France.
Her party is hoping to win two French regions in December local elections.
Outside court, the far-right leader insisted she had not committed any offence and questioned the timing of the trial.
“We’re a month away from a regional election and this affair dates back five years,” she told reporters.
Alarm at the rise of the National Front (FN) prompted President Francois Hollande to warn France not to take the risk of backing the far right.
“Don’t play with this way of voting just to send a message, just because of unhappiness and anger,” the president told French radio.
“For investors, for external trade, jobs and growth, there will be consequences.”
Marine Le Pen took over the FN leadership in 2011 and has since tried to steer the party away from its racist and anti-Semitic past.
It was during a campaign speech in December 2010 that she told FN supporters: “I’m sorry, but some people are very fond of talking about the Second World War and about the occupation, so let’s talk about occupation, because that is what is happening here.”
“There are no tanks, no soldiers, but it is still an occupation, and it weighs on people.”
The phenomenon of street prayers emerged when French Muslims were unable to find space in mosques, and after a political outcry the practice was banned in Paris in 2011.
Marine Le Pen was investigated for her public remarks and she was eventually stripped of her immunity from prosecution by the European Parliament in 2013.
Ahead of the trial, Marine Le Pen made clear that she would use the occasion to defend her right to freedom of expression.
She is accused of incitement to discrimination, violence or hatred towards a group of people because of their religious affiliation and if found guilty could face up to a year in jail and a fine of €45,000 ($51,000).
The French Council of the Muslim Faith said Marine Le Pen’s remarks had fed a climate of Islamophobia.