Prosecutions for motorists using a phone at the wheel are down by almost half in five years despite a study showing the potentially dangerous practice is more common, official figures show.
Data released by the Ministry of Justice last month show that just 17,414 prosecutions for drivers using their phone at the wheel were launched in magistrates' courts in England and Wales last year, down by 47% from 32,571 in 2009.
The fall comes despite a 2014 Department for Transport (DfT) study which found that 1.6% of drivers in England - more than half a million people - were observed using a mobile, up from 1.4% in 2009.
Mobile use is increasingly a contributory factor in accidents in Britain, according to the DfT. Latest figures show a 29% rise from 349 accidents in 2010 to 492 last year.
The analysis was carried out by the RAC, which claimed there was an "overwhelming frustration" among motorists that many drivers were "getting away with" using phones when they should be concentrating on the road.
The organisation's annual Report on Motoring found that over a third (34%) of drivers rank the dangers of talking, texting or using the internet on mobiles behind the wheel as one of their top concerns.
RAC head of external affairs, Pete Williams, said: "There is still an enormous gulf between what the law states - that handheld mobile phones should not be used behind the wheel - and what motorists see happening on our roads.
"Drivers are routinely using their phones at red traffic lights, or even while on the move."
Legislation was introduced in December 2003 to make it illegal to use a hand-held mobile while driving. Motorists caught are most likely to receive a fixed penalty notice (FPN) from a police officer.
Between 2011 and 2013 the number of FPNs handed to drivers dropped by 57% from 123,100 to 52,400, Home Office figures show. Drivers get three penalty points and a fine of £100.
A motorist may be summoned to a magistrates' court if they ignore or challenge an FPN, if they already have too many points or if the offence is deemed too serious for a fixed penalty.
Mr Williams warned that the reduction in full-time road policing officers has made it harder for the law to be enforced.
"On average across the country there was a 23% cut between 2010 and 2014 - meaning there are 1,279 fewer officers patrolling our roads," he said.
"Sadly, therefore, there are now far fewer police to enforce a law that is designed to protect all road users and pedestrians."
The House of Commons' transport select committee is conducting an inquiry into the effectiveness of road traffic law enforcement.
Mr Williams called for an end to cuts to the police budget and better use of technology to catch more offenders.
He also suggested that a national public awareness campaign could stigmatise phone use among drivers.
"The goal for ministers and policy-makers is surely to make the use of mobile phones at the wheel as socially unacceptable as drink-driving," he said.
"With this the number one road safety concern for motorists, coupled with official data showing fewer people are being caught, there will be an overwhelming frustration that too many drivers are simply getting away with it."
A DfT spokesman said: "It's illegal and dangerous for someone to use their phone for any reason while driving.
"To deter drivers from irresponsible behaviour, we introduced tougher penalties in 2013 and keep further measures under consideration."