France's Foreign Minister Jean-Yves Le Drian on Tuesday warned Turkey that concerns over security "absolutely do not justify" the scale of its offensive in Syria.
"Even if Turkey's concerns over the border are legitimate... this absolutely does not justify the action by Turkish troops deep inside the Afrin area," Le Drian told parliament.
"In no circumstances does it justify military operations that put civilian populations in danger," he added, branding the situation in Afrin "critical".
Turkey says its army and allied rebels have surrounded the Kurdish city of Afrin in northern Syria, raising the prospect of another devastating siege in the seven-year conflict.
Ankara launched its "Olive Branch" operation, aimed at ousting a Syrian Kurdish militia from Afrin, in January, escalating tensions with the United States and European NATO powers.
Turkey regards the YPG militia as a terror group and a branch of the Kurdistan Workers Party (PKK) which has waged a deadly insurgency on Turkish soil for three decades.
But the US-backed military coalition fighting the Islamic State group regards the YPG as a vital partner against the jihadists.
Le Drian said battling IS remained France's key motivation for its military involvement in the region, where it is part of the US-led coalition.
"It is a priority of national security and we fear that Turkey's action there will only weaken the pressure on Daesh's remaining resources in Syria," Le Drian said, using an Arabic acronym for IS.
"We have a very longstanding relationship with the Kurds and we recognise the essential role they played in taking back Raqa," he said in reference to the former IS stronghold, recaptured in October.