The commission was asked to analyse four energy policy scenarios to 2050. It said "intermittence" could cause problems "which should not be underestimated". These ranged from prolonging the life of France's current nuclear fleet to abandoning nuclear power completely.

The Energy 2050 report notes found increased deployment of wind and solar will require electricity storage on a "massive" scale alongside demand management.

The commission regards pumped storage as "useful but limited" and believes that even a Europe-wide grid does not exclude the possibility of several days without wind. In the absence of other competitive solutions, gas plants will provide the backup, it asserts.

While the country should continue to develop renewable energies, the commission recommends that "the optimal path" for France is to extend the life of its nuclear plants, as long as the Nuclear Safety Authority permits, and continue working on the next generation reactors.

The findings come in the wake of another report by the government auditors assessing the cost of France's nuclear programme. Given the timescale and financial situation, France had effectively decided to keep its reactors working beyond 40 years, the auditors said.