The prime minister's spokesman said that consultation on making "phoning and driving" an offence is to begin on Tuesday.

The law currently only prosecutes motorists using mobiles if they fail to keep proper control of their vehicle - there is no actual law specifically prohibiting the use of mobiles while driving.

Research suggests that people using mobile phones behind the wheel are four times more likely to have an accident than other motorists.

Everyone is so reliant on mobile telephones, you are not going to change this overnight

Jonathan Simpson, RAC Foundation

The Highway Code, which governs driving practice, says drivers should exercise proper control at all times and "never use a hand-held mobile phone" while driving.

Prosecuting employers

The Department of Transport's proposal for a new ban would toughen the laws on mobile phone driving still further.

The new regulations would also give police powers to prosecute employers who let their employees use mobiles in company cars.

But the legislation would stop short of banning hands-free phones, which would still be permitted.

Consultation will take place over a 12-week period, with motoring organisations and road accident lobby groups among those taking part.

The Home Office has already said it intends to make "driving without proper control of a vehicle" an endorseable offence which puts points on your licence, in addition to a fixed penalty.

Change of culture

The Royal Society for the Prevention of Accidents (Rospa) is backing efforts to make mobile phone driving a criminal offence.

It says mobile phone bans exist in 35 other countries and should be introduced in the UK.

Distance before braking response at 70mph

Normal driving - 31m Drunk-driving - 35m Using mobile - 45m

Jonathan Simpson, of the RAC Foundation, warned that a ban may not be enough on its own.

"Everyone is so reliant on mobile telephones, you are not going to change this overnight," he told BBC News 24.

He said more education was needed to alert people to the danger and bring about a change in culture.

At its conference earlier this year the British Medical Association also called for a ban.

Members quoted research carried out in Canada which showed a substantial increase in the number of accidents at times when mobile phones were being used.

It also showed little difference in the potential danger of hands-free phones and mobiles.