Australian Mark Webber labelled Red Bull as "toothless" after claiming the Formula One team could not control himself and ex-mate Vettel.
Webber - now plying his trade with Porsche in the World Endurance Championship - endured a tense relationship with Vettel, who defied team orders en route to a fourth F1 championship in 2013.
Recalling his time with Red Bull, Webber revealed he first noticed favouritism from the manufacturer's hierarchy in 2010.
"I've just won the previous two grands prix from start to finish and then a new rear wing arrives and goes over to the other side of the garage," the 38-year-old told ABC's Australian Story.
"And I know for a fact the mechanics were furious. You just think there was a bit of an agenda going on.
"They were very keen to keep [Vettel] probably a little bit happier because again, I was an old dog, I was the guy who was supposed to be a little bit washed up."
That was only a sign of things to come, as the pair's relationship completely soured in 2013, when Vettel disobeyed a team order, overtaking Webber to win the Malaysia Grand Prix.
With Webber leading in the closing stages in Sepang, Red Bull officials called for Vettel to back off from his pursuit, but the German defied orders.
"The team after Multi-21 were disappointed, no question about it, they were shown how toothless they were," Webber said.
"They couldn't handle us two out there on the track, which shouldn't be like that.
"[I was] furious with Seb a little bit. But the whole scenario was just 'how did we get ourselves in that position?'
"It was a pretty brutal press conference after the race and on the podium. We got off the podium and he just came over and said 'we need to talk, I've just fucked up, fucked up so bad'.
"I said 'mate well, let's just talk, let's talk next week'."
The incident ultimately prompted Webber to leave F1 for the World Endurance Championship at the end of 2013.
Webber added: "I don't know who spoke to him between Malaysia and China but we had a discussion in China and the discussion didn't go well.
"He just said that he had massive respect for me as a driver but not so much as a person, so that really affected the relationship.
"At the time, we could hardly stand the sight of each other.
"[Red Bull] just needed something to change so, you know, I helped that decision for them and left."
