Opposition leader Jean-Francois Cope called the intervention "just and necessary", in a parliamentary debate that underlined strong support across the political spectrum.
But Cope also admitted he was "extremely concerned that France should be so isolated”.
Cope told parliament: "When our soldiers are engaged, our hostages are threatened a spirit of national unity is required and takes priority over minor quarrels."
But he went on to question President Francois Hollande's diplomatic preparation for military action.
"Why have you not been able to put together a real coalition, as was the case in [the French-led intervention] in Libya in 2011?"
An intervention initially presented as limited to air strikes and the defence of the capital Bamako has escalated dramatically since the weekend.
French troops on Wednesday engaged Islamist fighters in western Mali, defence officials have confirmed that the ground force will grow rapidly to 2 500 men and air strikes have been extended to the north.
France's Nato allies have expressed strong moral support for the intervention and offered various forms of logistical support while ruling out sending any of their own combat troops.
In France, the action has been backed across the political spectrum, with the exception of the far left, and by 75% of voters, according to the latest poll.
Former president Valery Giscard d'Estaing said Hollande should have limited France's action to the defence of Bamako before the arrival of African troops.
"Airstrikes in the north and east of the country will hit the civilian population and repeat the pointless destruction of the war in Afghanistan with the same result," he wrote in Le Monde newspaper.
Destined to fail
His comments echoed those of Dominique de Villepin, a Gaullist former prime minister, who warned at the weekend that the Mali mission was destined to fail because its objectives were not clear.
Former Foreign Minister Alain Juppe described the deployment of ground troops as "extremely risky”.
"We have the means to do what we did at the start of the campaign, air strikes, but we certainly don't have the means to deploy in a territory two or three times as big as France," he told French radio on Wednesday. "They are at home in the desert. We are not."
Philippe Meunier of the UMP opposition party and a member of the parliamentary defence commission broke ranks with the party's leadership by claiming Hollande was directly responsible for the death of helicopter pilot Lieutenant Damien Boiteux, France's first casualty.
Meunier argued that the push south by Islamist fighters which triggered France's intervention had happened because Hollande had given them the impression he would not send combat troops.
"The repeated statements that France would only provide technical back-up for an African force convinced the Islamists to head for Bamako before they [the Africans] arrived," Meunier said.
That meant French forces were ill-prepared for the intervention, he added. "Our army had to go in with unarmoured helicopters, which resulted in the death of one of our pilots who was shot by a light weapon."
Green MP Noel Mamere also questioned the legitimacy of the action, distancing himself from the supportive stance of the leadership of a party that has a number of ministers in Hollande's government.
"It is said we responded to an appeal from the president of Mali, but isn't this president a mere puppet of the military who will not hesitate to overthrow him?" Mamere said.
Hollande said on Wednesday he would allow parliament to vote on military action in Mali if the intervention lasted more than four months, as required by the constitution.