Drivers could be prosecuted for smoking if they are judged not to be in full control of their vehicle, according to the latest version of the Highway Code, released on Friday.
Road Safety Minister Jim Fitzpatrick said the new Highway Code is "a crucial tool for all road users" but the AA motoring association warned that the new guide is more complicated than previous editions and contains 29 more rules.
AA spokesman said: "After an eight-year gap since the last edition, it would have been helpful to have had the changes marked out, as they were in the draft, and allow experienced drivers to skim through this 307-point version.
"A major change is the code's inclusion of smoking at the wheel as behaviour that police may interpret as a distraction and failure to be in proper control of the vehicle. This addition will polarise drivers' opinions both for and against," he added.
The code has also been updated to include new legislation on vehicle emissions and a new section for novice drivers.
It informs those who have only just passed their driving test: "If you are driving with passengers, you are responsible for their safety.
"Don't let them distract you or encourage you to take risks. Never show off or try to compete with other drivers, particularly if they are driving badly."
And Fitzpatrick emphasized that all road users should know the rules, whenever they started driving: "The Highway Code is for life, not just for passing your driving test.