Motorists who use hand-held mobile phones while driving have been warned they could be issued with fixed penalty notices in Cumbria.
The new ban came into force this week and carries a £30 fixed penalty fine or a maximum fine of up to £1,000 for conviction in court, rising to £2,500 for drivers of goods vehicles, buses and coaches.
The Association of Chief Police Officers had suggested that forces in England and Wales "might consider" issuing verbal warnings to drivers for the first two months.
But ACPO also said officers could "use their discretion to take formal enforcement action in individual cases" if the offence was "serious" or "contributed to a collision".
Cumbria Police spokesman Mike Head said the message to drivers was not to use mobiles at all while driving as they could cause a distraction.
Mr Head said: "Officers will use their discretion in applying the legislation over the next few weeks. Before this recent legislation was brought in, it was an offence not to be in full control of their vehicles, and if officers come across such a case they will continue to apply the appropriate penalty."
Mr Head said: "Our advice is don't use a mobile phone while driving as there is a strong chance you will be penalised if you do. We may still issue fixed penalty tickets but we will use our discretion."
Lancashire and North Yorkshire police said they were prosecuting where appropriate but otherwise warning drivers.
North Yorkshire spokesman Ron Johnson said: "We will not be prosecuting everyone from day one and our tendency will be towards warning people initially, but if someone is using a phone and driving dangerously then we will have the option of taking criminal proceedings."
The ban makes it an offence for a person to drive a vehicle on a road if they are using a hand-held mobile phone, including when stopped in a traffic jam.
The only exception is to make 999 emergency calls or where it is unsafe and impractical to stop and pull over to make a call.
Some hands-free kits are allowed but mobiles must be fitted to a cradle and police advise that people can still be prosecuted if they commit an offence while using a phone.
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