The OECD said: “Significant efforts will be required to stabilise France’s public debt at close to 120 percent of GDP in 2060.”
Steps need to be taken to offset the costs of the nation’s ageing population, it said.
It added: “The debt-to-GDP ratio will remain close to 120 percent of GDP and could rise to close to 150 percent of GDP in 2060 if the rise in interest rates proves greater than projected.
“That would threaten the viability of the public finances.”
Debt levels in France currently stand at 115 percent of its GDP, which compares to almost 160 percent in Italy.
French workers can start drawing a state pension from the age of 62 meaning they typically contribute for roughly 33 years – but can expect to live for 26 years during retirement.
France spends 14 percent of GDP on public pensions, compared with 10.2 percent in Germany.