A new law which comes into force on Monday will see motorists who cause fatal accidents by using a mobile telephone at the wheel face up to five years' imprisonment.
The long-awaited new offence of causing death by careless driving is designed to plug a hole in current legislation, the Ministry of Justice said.
It means that motorists will face tougher penalties if they kill because they were "avoidably distracted". Such distractions could include calling or texting on a mobile phone, drinking or eating, adjusting a satellite navigation system or car stereo, applying make-up or reading a map.
Judges will be able to impose a maximum sentence of five years' imprisonment, although they could opt for a lesser community sentence, even in the medium category of seriousness.
Another new offence will come into force on Monday which penalises uninsured, disqualified or unlicensed drivers who kill, carrying up to two years' imprisonment.
About 150 motorists a year are expected to be jailed after being convicted of the death by careless driving offence, and about five a year for the "uninsured" offence.
© The Press Association 2008