Fillon and Juppé both stayed away from direct attacks on their rivals, choosing instead to try to present a unified Les Républicains party ahead of next year's presidential election.

Thursday's evening's debate, which was broadcast live on French TV, ranged widely and emphasized policy prescriptions for reviving France's sluggish economy and to bring down unemployment.

Both candidates supported, with small differences, measures to make working hours longer and more flexible and to increase the retirement age.

They both advocated deep cuts in public spending, tax cuts, and reforms to the public sector to shave down the budget.

Fillon's plans go further

Sixty-two-year-old Fillon, who has proposed expanding France's famous 35 hour working week to 48 hours, said his plan would still allow workers to refuse longer hours.

"Alain Juppé does not really want to change things. He's staying within the system, he just wants to improve it," Fillon told viewers. "My project is more radical."

But the 71-year-old Juppé hit back, saying: "Reform should not be a punishment but bring hope. The French social model exists, I want to consolidate it," he added, referring to the country's welfare safety net. "We should not break it."

Juppé is backed by France's two main centrist parties and is relatively popular among left-wing voters.

Contrasting views on multiculturalism

Perhaps the biggest point of difference was on a question of multiculturalism in France, where Juppé suggested that a country composed of people from different backgrounds and skin colors was a strength. Fillon, meanwhile, said it was vital that new arrivals adapted to France, and subscribed to its values.

Thursday's broadcast was the second of two debates. Last week, Fillon swept to the front of the race in the party's first-round primary election.

The first vote saw former president Nicolas Sarkozy knocked out of the race to return to the Elysee Palace.

Latest poll favors Fillon

In an online survey by Elabe pollsters, of nearly a thousand people who watched Thursday's televised debate, 71 percent of conservative and center-right voters found Fillon more convincing than Juppé.

Fillon was also ahead among all viewers independent of their political stripe, but by a smaller margin, with 57 percent versus 41 percent for Juppe.

The winner of Sunday's vote will stand a good chance of being elected president in May, analysts said.

Les Républicains, formerly the Union for a Popular Movement (UMP), could benefit from deep divisions on the left of French politics and opinion polls showing a majority of voters are opposed to seeing the far-right Front National in power.

Current President Francois Hollande is suffering from record low public support. His Socialist party will hold its own primary contest in January, ahead of the first round of the presidential election, on April 23.

mm/jm (AFP, Reuters)