Northern Ireland motorists caught using a mobile phone while driving will be shown a "yellow card" by police.
Using a hand-held phone while driving will become an offence
The scheme comes into effect from Sunday.
However, from the beginning of March drivers will get a "red card".
Environment Minister Angela Smith said using a mobile phone while driving affected the ability to concentrate and anticipate the road ahead.
"Research has shown that if you drive and use a mobile phone, you are four times more likely to have a collision and nine times more likely to be in a fatal collision," she said.
"That is why, from 1 February 2004, we are introducing new legislation prohibiting the use of a hand-held mobile phone while driving."
MOBILE PHONE LAW
Drivers are nine times more likely to be in a fatal collision
Drivers face a non-endorseable offence subject to a fixed penalty of £30 or a fine on conviction of up to £1,000
New legislation next year will make it an endorseable offence, attracting penalty points and a £60 fine
Causing death by dangerous driving could lead to a prison sentence of up to 14 years
Drivers still risk prosecution for failure to have proper control if they use hands-free phones when driving
The new regulations apply to the drivers of all motor vehicles on the road, including cars, motorcycles, goods vehicles, buses, coaches and taxis
There is an exemption for calls to 999 (or 112) in genuine emergencies, where it is unsafe or impractical to stop
Initially, offenders will be subject to a £30 fixed penalty, which can be increased to a maximum of £1,000 if the matter goes to court.
The maximum fine for drivers of vans, lorries, buses and coaches will be £2,500.
Throughout February, the police in Northern Ireland are to show the yellow card to drivers who use a hand-held mobile phone while driving.
However, from 1 March, police will rigorously enforce the new legal ban on mobile phones with a red card.
Inspector Rosemary Leech of
the Police Service's Road Policing Development Branch, said it was also unacceptable for a passenger to hold a mobile phone to the driver's ear.
"This brings us into line with the rest of the United Kingdom, where the law changed in December," she said.
"While there has been significant coverage in the press about the new legislation, police are allowing the next month as a period for advice and warning.
"This is not carte blanche for motorists to continue to use their hand-held mobile phones, without any thought. It is to give them time to get used to the fact that they must not use hand-held mobile phones while driving."
The Royal Society for the Prevention of Accidents (RoSPA) urged Northern Ireland motorists not to risk breaking the new law.
It also backed drivers being prohibited from using hands-free phones as well.
Kevin Clinton, RoSPA Head of Road Safety, said: "We are delighted to see the new law, but it will not have the impact in Northern Ireland we have been hoping for if people switch to hands-free devices instead.
"It is the telephone conversation that is the main problem. People are drawn into the conversation and ignore what is happening on the road around them.
"They vary their speed, drive closer to other vehicles, wander about on the road and their reactions are slower."
RoSPA said it was aware of at least 23 deaths on UK roads where mobile phones had been implicated.
People should switch off their phones when they get into their vehicles and not use them again until they are parked in a safe spot, said the society.