France's Prime Minister Jean-Marc Ayrault delivers his speech during a parliamentary debate on Syria at the National Assembly in Paris. (CHARLES PLATIAU/Reuters)

France will not launch a military assault against Syria by itself, Prime Minister Jean-Marc Ayrault said Wednesday, amid calls by French opposition leaders to put any action to a U.N. Security Council vote.

During a raucous two-hour parliamentary debate, French lawmakers argued about the wisdom of acting against Syria after President Obama decided to seek congressional approval for a U.S. strike. Allies of French President François Hollande accused Syrian President Bashar al-Assad of repeatedly using chemical weapons against his citizens and said that if the world did not respond with force, he would do so again.

But opposition leaders said France would be in contravention of international law if it acted against Syria without U.N. authorization — an unlikely development in any case because of Russia’s veto power in the Security Council and its implacable opposition to any move against its longtime Syrian ally.

“We are certain that Syria has at its disposal the most important stockpile of chemical weapons in the world,” Ayrault told France’s lower house of Parliament. “Not to respond” to an alleged Aug. 21 chemical weapons attack, he said, “would be to send a terrible message to Bashar al-Assad and to the Syrian people: that you can use chemical weapons tomorrow.”

But many opinion polls in recent days show a lack of public support here for a strike against Syria. Under the French constitution, Hollande has broad powers to order military action without consulting Parliament or submitting to a vote. Still, many opposition leaders said Wednesday that they want, at a minimum, to vote on such a decision, a course of action that had 74 percent support in a CSA opinion poll released Tuesday.

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Leaders of the main center-right opposition Union for a Popular Movement party (UMP) went further during Wednesday’s debate, saying that France would be breaking its long-held commitment to acting in accordance with the United Nations if it proceeded without a Security Council vote and that it was humiliating for France to stand alone as it waited for allies to assemble around it.

“France should not be in the position of waiting with its arms crossed for a vote of the U.S. Congress,” said Christian Jacob, president of the UMP faction in the lower house.

“The United States is used to going alone and not going along with the U.N.,” he said, but he noted that France is different. “Nothing justifies this radical change in the diplomatic stance of France.”

Hollande’s allies have said that no decisions on French military action will be taken before the U.S. Congress votes next week.