Top French banker: Le Pen's euro exit would cost billions

France's central bank chief says that presidential candidate Marine Le Pen's proposal to leave the euro currency would cost the country more than 30 billion euros ($32 billion) a year in extra debt interest.

Francois Villeroy de Galhau vigorously defended the euro on France-Inter radio Monday, warning voters not to believe Le Pen's nationalist promises of stronger purchasing power if France abandons the shared currency.

Villeroy de Galhau said leaving the euro would unleash high inflation, devastating individuals' savings.

A major question is how Le Pen would handle France's considerable debt. She said last week she would redenominate most of it into a new currency.

The central bank chief estimated that the extra debt interest would be over 30 billion euros a year, roughly equivalent to France's entire military budget.