France’s state audit body has said that EDF Energy should ask itself “serious questions” before moving ahead with the huge multi-billion pound project to build Hinkley Point C near Burnham-On-Sea.

The Cour des Comptes said on Thursday that the “complexity of both funding and carrying out” the £18bn project should lead to the nuclear group and the French state asking if it is the right plan.

The regulator’s comments add to the voices opposed to the controversial nuclear deal, just days after EDF chief financial officer Thomas Piquemal resigned over concerns that Hinkley Point C could threaten the company’s future.

The Cour des Comptes, a public spending watchdog, did not say that the Hinkley project is a mistake and made supportive points as well, praising in particular the high guaranteed electricity price – or strike rate – agreed with the government.

The criticisms contained in the report will not be welcomed by EDF, which is close to making a final investment decision which will then commit it to spending around €15bn over 10 years.