According to the highway code and all. It says, over and over again, that talking on the phone, using the phone at all, changing radio stations, using a satnav - all these things will take your attention off the road. But hey, DRIVING. It's more important.
Even hands free is dangerously distracting according to at least one study..... http://www.sciencedaily.com/releases/2013/06/130612092949.htm