PARIS (AP) -- French Prime Minister Michel Barnier is bracing for a no-confidence vote this week, a political reckoning almost certain to topple his fragile government and send shockwaves across the eurozone.

Barnier on Monday invoked a rarely used constitutional mechanism to push through the contentious 2025 budget without parliamentary approval, arguing it was essential to maintain "stability" amid deep political divisions.

The move immediately drew sharp backlash, with Marine Le Pen's far-right National Rally and the leftist New Popular Front both filing no-confidence motions in response, setting the stage for a vote as early as Wednesday that could see Barnier's ouster.

The looming showdown unfolds against the backdrop of a fractured National Assembly, left in disarray after June's snap elections delivered no clear majority.

President Emmanuel Macron had turned to Barnier in September to navigate the impasse and address France's soaring deficit. Yet Barnier's proposed austerity budget -- slashing 40 billion euros ($42 billion) in spending and raising taxes by 20 billion euros -- has only deepened divisions, inflaming tensions in the lower house and triggering this dramatic political confrontation.

The use of the constitutional tool, called Article 49.3, allows the government to pass legislation without a parliamentary vote but leaves it exposed to no-confidence motions. Opposition leaders argue that Barnier's concessions, including scrapping an electricity tax hike, do not go far enough to address their concerns. Le Pen accused Barnier of ignoring her party's demands.

"Everyone must shoulder their responsibilities," she said.

The political standoff has unsettled financial markets, with borrowing costs rising sharply amid fears of prolonged instability. Barnier warned of "serious turbulence" if the budget isn't passed, but critics dismissed his remarks as fear-mongering.

If the no-confidence motion succeeds, Macron will remain president but will need to appoint a new prime minister to steer legislation through the fractured assembly. The uncertainty threatens to deepen France's economic troubles and reverberate across the eurozone.