Former world champion Nigel Mansell has warned Lewis Hamilton it could be a mistake to leave McLaren for Red Bull.
Hamilton has again been linked with a move to the champions, in the build-up to Sunday's British Grand Prix.
But Mansell argues Hamilton, 26, should bide his time with McLaren, who guided him to the 2008 title, saying: "It might be a mistake if he changes team.
"He hasn't exactly had a drought. I'd stay with McLaren and the people who've supported him in thick and thin."
Speculation that Hamilton was actively seeking a move to Red Bull gathered pace when he had a private conversation with Red Bull team boss Christian Horner in the paddock at last month's Canadian Grand Prix.
The McLaren driver, whose contract expires at the end of 2012, said recently that he had "never thought of myself in a Red Bull car".
Despite that, Hamilton is understood to be uncertain about his future at McLaren because they have failed to deliver the fastest car in the field for the last three seasons running.
But Mansell, who won the 1992 championship in his 13th season in the sport, has counselled against making any rash decisions.
"You'd have to be fortunate to be offered [a Red Bull drive] but for me Lewis has had an amazing career with McLaren," Mansell added.
"Michael Schumacher proved by staying with Ferrari if you can have the support of a team totally behind you, then you can build on that year on year."
Hamilton has fallen to fourth in the standings and is 89 points behind leader Vettel going into the ninth race of the season this weekend in Britain.
The Englishman was involved in four collisions, at recent races in Monaco and Canada, and Mansell has advised the driver not to change his attitude but to tidy up his driving style.
"Lewis is a racer and a fighter but the thing he hasn't got quite right is when you pass people, don't try and knock them off!" he said.
"Still go for the gaps but give them a little room and don't do it on corners where there is no recovery.
"He's just got to get it a bit more right than what he has done in the last few races."
Hamilton's team-mate Jenson Button is the closest man to Vettel in the title race but he is still 77 points adrift - more than the equivalent of three race wins.
With 11 races to go, Mansell has encouraged Vettel's rivals not to lose hope but to raise their own performances and pile pressure on the German world champion.
"Never give up and stop making those small mistakes from Thursday onwards because if you make one small mistake under the current rules it puts you on the back foot," advised Mansell. "Everything has to be perfect.
"Sebastian has made less mistakes than any other driver this year, he is defending the world championship in a far better manner than he won it, he's matured beyond all belief and he is riding the crest of a wave and doing a fantastic job.
"It's up to everybody else to do a better job and to start beating him."