Alain Prost: 2014 changes were essential for Formula 1

The four-time F1 world champion, who is an ambassador for French car manufacturer Renault, is upset that leading figures like Bernie Ecclestone and Luca di Montezemolo have been so quick to rubbish the new fuel-efficiency regulations.

Speaking during a Formula E test day, Prost said: "I'm really negative about the comments that have been made about Formula 1 in the last few weeks, because I don't think it's very fair.

"When you are involved in F1, you should not make such negative comments. For sure, Bernie has never been in favour of [the new rules] but I was more surprised by Luca.

"I can't understand, because everybody should be going in the same direction."

Prost said that those speaking out against the current rules have forgotten how F1's popularity has been in decline in recent years.

He believes the sport needed a shake-up to try to generate more interest.

"People forget that the audience was going down in the last two or three years," he said. "Teams appear to have difficulties to find sponsors, and that's not because of these new regulations.

"I have had some discussions with some top Renault people in the past two years and I'm not convinced Renault would have stayed in F1 without changing the technology.

"I'm not sure that Honda would have come back [for 2015]. It was the way to go, in my opinion.

"We had to do it. Sometimes, when you're at the end of a cycle, you need to have something new. And you need to wait and give new technologies time to get used to it."