Kimi Raikkonen is not about to quit in the middle of a Formula 1 season.
There are reports the 2007 world champion lost his cool over the radio several times during the most recent Silverstone weekend, as Alfa Romeo battles with Williams and Haas to avoid the ignominy of being F1's slowest team.
"Of course Kimi is frustrated," Lehto told Iltalehti newspaper.
"But the car is awful. It has no downforce at all, it's sliding all the time. It's a real burden for a driver of Kimi's level."
However, Lehto does not think Raikkonen is about to retire mid-season.
"No, Kimi isn't going to give up in the middle of the season. He will finish the season for sure."
Lehto was also asked about Romain Grosjean, amid suggestions the Haas driver was inappropriately aggressive whilst defending during the British GP.
"The guy's driving tactics were incomprehensible," said the former Benetton driver. "Moving under braking like that is the last thing you should do on a race track. He could easily have caused a big accident.
"It was life-threatening and really silly," Lehto added.
As for Grosjean's team Haas, Lehto thinks it is very possible that owner Gene Haas will pull the plug at the end of the season.
"He already said that before the season, and at the moment I can't see many reasons to fund such an expensive project when you're not really getting any kind of result," he said.