Calls for mobile phones to be banned from cars altogether have come from an experts at Sussex University.
The use of handheld phones while driving is already banned
Dr Graham Hole said vehicles have been transformed into "mobile offices", with satellite navigation, telephones and other devices.
He said even hands-free sets had failed to make the roads safer.
The problem with mobiles was not having only one hand on the wheel, but taking away attention from what is happening outside the car, he said.
His research, called The Psychology of Driving, which includes a look at the spread of modern in-car technology, is due to be published next month.
In 2003, a ban came into force on using handheld mobile phones while driving.
Hands-free kits were still allowed, but many road safety experts said they did not reduce the risks of having an accident.
Road safety charity Brake called for a ban on the use of all phones by drivers, saying hands-free kits did not make driving safer.
The AA Motoring Trust said drivers using mobiles were four times more likely to have an accident, even if they were employing hands-free devices.
But it said a ban on hands-free devices would be extremely difficult to enforce.