More than 95% of people are unable to drive safely while talking on a hands-free mobile phone, researchers have claimed.
Scientists at the University of Utah said motorists using the equipment took 20% longer to apply the brakes in a driving simulation and were 30% worse at keeping up with a vehicle when asked to follow it.
Just 2.5% of people, labelled "supertaskers", who took part in the study were able to drive and talk on a hands-free kit without any impairment.
Study leader Jason Watson said: "Given the number of individuals who routinely talk on the phone while driving, one would have hoped that there would be a greater percentage of supertaskers.
"The odds of being a supertasker are about as good as your chances of flipping a coin and getting five heads in a row."
Brake campaigns officer Ellen Booth added: "The evidence is overwhelming. Using a hands-free or hand-held phone while driving is dangerous, full stop.
"It's time that our politicians took note and put an end to the ridiculous situation where using a hand-held mobile is banned, but using hands-free isn't."
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