The former McLaren driver David Coulthard says Lewis Hamilton needs someone around him to offer sound advice and should appoint a new manager as soon as possible to replace his father.
Hamilton announced last month his father Anthony was stepping down as his manager to focus on his own business interests but Coulthard says the decision appeared to be backfiring.
The Scot says the folly of not appointing a replacement showed over the weekend when Hamilton made the headlines in Melbourne after police stopped him for driving in what he called an "over-exuberant" manner.
The 25-year-old Briton also castigated his McLaren team during the race for calling him in for a second pitstop while chasing for second.
He ended up sixth with world champion team mate Jenson Button winning.