PARIS — The two dynamic and very different candidates to be France’s next president faced off yesterday in their first and last televised debate of the campaign, a highly anticipated encounter before the weekend vote, and sparks flew almost from the start.

Socialist Ségolène Royal, struggling in her quest to become France’s first female president, immediately went on the offensive, criticizing conservative Nicolas Sarkozy’s record as a minister in President Jacques Chirac’s government before he became a candidate for the presidency.

Mr. Sarkozy, leading in the polls and looking to get through the debate unscathed, was scrupulously polite and did not rise to Ms. Royal’s baiting. He addressed her as “madame” and, after she repeatedly interrupted him in a discussion about policing and crime, said, “Will you let me reply?”

Ms. Royal wore a dark jacket; Mr. Sarkozy, a suit and tie. But their differences were more than one of style. An immediate point of disagreement was France’s 35-hour work week — a landmark reform for socialists but decried by business leaders as a crippling brake on companies.

Mr. Sarkozy wants to get around the 35-hour week by making overtime tax-free to encourage people to work more. He described the shortened work week as a “monumental error” and noted that no other country in Europe has followed France’s lead.

Ms. Royal defended the 35-hour week as a form of social progress and asked why the government of which Mr. Sarkozy was part had not gotten rid of the legislation if it was so opposed. Again, Ms. Royal cut Mr. Sarkozy off during the discussion.

“Will you let me finish?” he asked.

“No,” said Ms. Royal.

“Ah,” said Mr. Sarkozy.

The live duel by candidates drew more than 20 million viewers in a nation re-energized by its hunger for change after 12 years under Mr. Chirac.

“It’s the culmination point of the campaign,” a former president, Valery Giscard d’Estaing, who supports Mr. Sarkozy, said on RTL radio. He said the debate would be “decisive,” and credited his own performance in a debate with socialist Francois Mitterrand for his victory in 1974. Mitterrand won the presidency in 1981.

Mr. Sarkozy and Ms. Royal were the last two candidates standing after the April 22 first round in which Mr. Sarkozy won 31.2% and Ms. Royal had 25.9%, with 10 rival candidates across the political spectrum taking up the remainder.