France's brewing political crisis is spilling into financial markets with French borrowing costs hitting the same level as debt-ridden Greece's for the first time.

The European Central Bank is once again facing questions over whether it would shore up France's rattled bond market as Prime Minister Michel Barnier is facing a budget test that could topple his unpopular government.

Borrowing costs for France hit a 12-year high relative to Germany, and were equal to those of Greece for the first time ever

French 10-year bond yields, which move inversely to prices, rose as high as 3.022 per cent in early trading, taking them marginally above Greece’s yields at 3.013 per cent. Greek yields later dipped to 2.

French borrowing costs effectively matched those of Greece on Thursday for the first time, as Michel Barnier's government teetered on the brink of collapse, underlining a dramatic shift in how lenders view the creditworthiness of euro zone members.

French borrowing costs have exceeded those of Greece for the first time, as Michel Barnier’s government teetered on the brink of collapse. Hard-Right and Leftist opposition parties have been threatening to bring down Barnier’s government over its budget that includes €60bn (£47bn) in tax hikes and spending cuts.