FIA technical official Nikolas Tombazis has admitted the 2019 rule changes will not 'fix' formula one.
There is widespread scepticism about claims the car design tweaks for next year will make overtaking easier.
"Honestly, after our work in the simulator and the wind tunnel, we do not believe it will become easier to overtake," said Renault boss Cyril Abiteboul.
Former Ferrari designer Tombazis, who recently joined the FIA, admits that the changes are not a magic solution.
"The current generation cars mean the one following loses about 30 per cent efficiency," he told France's Auto Hebdo.
"We hope to reduce that by 10pc. It's difficult to say an exact figure, but the fact that the teams develop more and more downforce exacerbates the problem.
"If we had not intervened, we think that in 2019 it would have been worse than in 2018 and 2020 would have been worse than 2019," he said.
"We now think that 2019 will be much better than 2018, but no one expects F1 cars to not be F1 cars anymore."
