The measures being published by the Crown Prosecution Service (CPS) could also see motorists in England and Wales who cause death on the roads facing life imprisonment.

Detailed guidance on the harsher measures, which were announced earlier this year, telling prosecutors when to bring manslaughter charges, will be outlined in the policy document.

They mean the very worst cases of death by dangerous driving could instead be prosecuted as manslaughter, which carries a maximum life sentence.

Using a mobile phone, sat-nav or an MP3 player while at the wheel will be treated as dangerous driving instead of careless driving, with the chance of up to two years in prison.

Dangerous driving comes with a two-year maximum prison sentence, whereas careless driving can only be dealt with by a community order or a fine.

Director of Public Prosecutions Ken Macdonald QC said, when the measures were first announced in September: "We accept that in cases where there is clear evidence that danger has been caused by their (mobile phones) use - such as texting while driving - then our policy should spell out that the starting point for charging will be dangerous driving."

Current guidelines say manslaughter is "very rarely appropriate" in road death cases but the change will mean alternative charges could be brought against one motorist.

For example, someone who has killed on the roads could be charged with manslaughter as well as causing death by dangerous driving, leaving a jury open to return the lower charge if they find manslaughter has not been proved.

Last year's consultation paper said other aspects of bad driving may also need to be treated as dangerous driving and carry a jail term, including tailgating, tuning a car radio, "undertaking", running a red light and applying make-up or lighting a cigarette on the move.