Jean-Eric Vergne says he cannot understand why Red Bull decided not to promote him into its leading Formula 1 team next season.
The Frenchman found out last week that he would lose his Toro Rosso race seat to Formula Renault 3.5 champion Carlos Sainz Jr for the 2015 F1 campaign.
Vergne hoped Red Bull would favour using him as a benchmark to help Formula 3 rookie Max Verstappen progress faster when the teenager becomes the youngest driver ever to race in F1 next year.
But the decision to promote Sainz alongside Verstappen, allied to Russian Daniil Kvyat's move to partner Daniel Ricciardo at Red Bull, means Vergne will be without a Red Bull-backed race seat in F1 next season.
Rookie Kvyat outqualified Vergne 12 times in 19 races this year, but finished 14 points worse off in the drivers' championship.
Verne told AUTOSPORT a weight disadvantage had affected his qualifying form against Kvyat, and said he could not understand why his points total has not been enough to get him promoted to the leading Red Bull team alongside Ricciardo.
"Nothing has made any sense," Vergne told AUTOSPORT when asked about the decision to promote Kvyat ahead of him.
"Last year I know [the reason I lost out on a Red Bull drive to Ricciardo], this year I guess there is some politics. I don't know.
"They [Red Bull] always say points matter; they know I was 5kg overweight compared to my team-mate, so I had at least two tenths [disadvantage] that no one knew about in qualifying - they know all the technical issues I had that didn't allow me to score points.
"I think I've made a really strong season compared to last year and I think it's been really unfortunate that I've had so many [technical] problems, because I would have had a lot more points and things would play a different role for me.
"I think I made a massive step forward compared to last year and I feel much better and happier as a driver.
"I have nothing to regret. There are many things I cannot say that never played in my favour, but that is how it is.
"I always try to get stronger every time something comes against me."