The current law regarding mobile phone use in vehicles only covers the use of a handheld telephone. Hands-free kits with voice-activated dialling and answer are available that make it perfectly legal to use your telephone whilst driving, but that does not make it safe.
A recent study in Sweden considering the growing research base on the subject concludes: "There is no evidence suggesting that hands-free mobile phone use is less risky than handheld use. Nevertheless, a large percentage of drivers think that handsfree sets are much safer to use than handheld sets.”
Using a mobile telephone in the car leads to an increase in reaction times and also in the number of 'missed events'.
If your telephone is ringing and you need to answer the call, find a safe place to pull over and turn off the engine before you pick up the telephone.