The number of drivers convicted of the offence has almost halved to just under 12,000 between 2012 and 2016, figures from the Ministry of Justice show, while in the decade to 2017, the number of traffic officers in England and Wales fell by nearly a third, from 3,766 to 2,643.
Nick Lyes, from the RAC, said: “If there are less police officers on the road enforcing the law, that means there is probably less prosecutions taking place as well.
“We are concerned that our most recent data shows that bad habits are creeping up again.”
There was a lot of work to be done if drivers’ attitudes to using mobile phones at the wheel are to change, he said.
“What we have got to do in this country is to make the use of a handheld mobile phone whilst driving as socially unacceptable as drink driving,” Mr Lyes added.
Figures from the RAC show a quarter of drivers admitted to talking on a handheld phone while driving, and 40 per cent of drivers confessed to texting at the wheel.
The research also shows that there were nearly 2,300 crashes caused by drivers using a mobile phone between 2013 and 2017.
In 2017 alone, 33 of these crashes were fatal.
David Kirk, from Horncastle, Lincolnshire, was killed in 2016 when a distracted driver, on her phone, veered onto the wrong side of the road and knocked him off his motorbike.
His widow Katie Kirk urged motorists not to drive while using a phone, saying: “I just want people to think. It’s not worth it. What it can do to someone. It’s just stupid.”
According to the BBC Inside Out programme, officers put on double decker buses to catch drivers using their phone have sometimes seen them spot so many offenders in other vehicles that officers cannot record their details quickly enough.