Whitmarsh admitted that he does “not fully understand” why the former world champion opted to end a 14-year association with McLaren and join a side that has won just one race in three years since returning to the sport.
Further, Whitmarsh accepts that Hamilton may wish to “to flee the nest” but remains disappointed by the move, especially as he feels it was made after a bad day at Singapore that saw him drop out on lap 23 with a gearbox failure.
Whitmarsh said: “I respect his decision, but I believe he would be better off with us.”
Despite signing a three-year deal worth £45 million with Mercedes, Hamilton has already spoken of the challenges he will face next term in a car significantly slower than his current drive.
Asked whether Hamilton already regretted his decision Whitmarsh added: “I think he has on occasions, yes.
“I hope he thinks today he’s made an awful mistake and I hope he thinks that next year.”