Prosecutions will be brought if by using the equipment a motorist is judged to have posed a danger to other drivers, such as causing another car to swerve.
Using a hand-held mobile while driving was outlawed in 2003, but it is estimated that half a million motorists flout the ban each day.
Existing guidelines restricted prosecutors to pursuing only a charge of careless driving, for which the maximum fine is Â£5,000 along with up to nine points on a motorist's license.
But under the new rules, drivers could be charged with dangerous driving, which carries a maximum sentence of two years in jail.
It is believed that by increasing the penalties, drivers will start to take the law seriously.