McLaren risk destroying the career of rising English star Lewis Hamilton by promoting him to their Formula One team in 2007, according to David Coulthard.
If Lewis struggles alongside Alonso it could destroy his confidence
The Scot, a McLaren driver from 1996-2004, said Hamilton's career and confidence could be wrecked by world champion team-mate Fernando Alonso.
"I believe McLaren have given him his break way too soon," Coulthard told the News of the World.
"He could face a very tough time with Alonso as his team-mate."
Coulthard said Hamilton, 21, would have been better off spending a year learning about Formula One as a test driver before being given his chance - a route Alonso took with Renault.
"Alonso may be new to McLaren but he is a double world champion," Coulthard said. "The first person you are compared to is your team-mate and if Lewis struggles alongside Alonso it could destroy his confidence."
The 35-year-old Red Bull driver added: "It's great for Lewis to be the first black driver in F1.
Hamilton has been given his break by McLaren boss Ron Dennis
"I've known him since he was a kid in karting and I have absolutely no doubt he has the right attitude and work ethic to be successful in F1.
"But he would have been better off with a year's testing. He is still only 21 and has plenty of racing years ahead of him.
"There is no doubting his potential. But he needs time to develop - not just as a driver, but also as a man.
"I was 24 when Williams gave me my Grand Prix chance after Ayrton Senna was so tragically killed at Imola.
"But I had already had three years testing and preparing myself.
"I still made mistakes on the track, as well as in life, because I was still trying to live my life and race cars.
"I understand that Lewis is desperate to race, but he would have been better armed to deal with all the pressure through the benefit of experience."