Drivers on mobiles 'often texting or on internet'
People who use their mobile phones illegally while driving are more likely to be sending texts or using social media than making a phone call, the Department for Transport says.
It carried out observations at 60 sites in five areas of England and 30 locations in Scotland last October.
Overall, the DfT found 1.1% of drivers holding a mobile in their hand compared with 0.5% with a phone to their ear.
Van drivers used their phones the most, with 2.7% falling foul of the law.
Legislation was introduced in 2003 making it illegal to use a hand-held mobile phone while driving or riding a motorcycle.
Drivers may be issued with a fixed penalty notice, resulting in three penalty points on the driving licence and a fine of £100. If a case goes to court, they face disqualification and a fine of up to £1,000.
The use of hands-free phones is permitted but a driver can still be stopped if police believe they are distracted.
The DfT says the purpose of its surveys in South East England, Manchester, Newcastle, Durham, Norfolk and Scotland was to "assess compliance".
Observations were made of drivers of cars, vans, taxis, lorries, buses, minibuses and coaches between 07:30-12:00 and 13:30-18:00 on weekdays. Some locations were surveyed again at weekends.
The DfT said: "A distinction was made between drivers holding the phone to their ear (indicating that the driver was receiving or making a call) or holding it in their hand (indicating that the driver may have been receiving or making a call, texting or reading a text, or using it for some other interactive function)."
It acknowledged that "it was not possible for observers to determine what the mobile phone was being used for".
However, it said the finding "suggests that most mobile phone usage whilst driving was for the purposes of sending or receiving a text or using social media rather than making a call".
Among car drivers, 1.4% were found to be using a mobile.
Although 2.7% of van drivers were using a phone, most (1.9%) were holding it to their ear rather than in their hand.
Only 1.2% of goods vehicles and lorry drivers were on a phone, with bus, coach and minibus drivers having the lowest usage rate at 0.4%.
Officials spotted 1.7% of male drivers using a hand-held mobile phone, compared to 1.3% of females.
The DfT said the proportion of car drivers in England observed using a mobile was about the same as in 2009, when a previous survey was carried out.
Transport minister Robert Goodwill said: "No phone-call is worth risking an accident. This research shows that the problem isn't just drivers making phone calls, it is their use of phones to text or use the internet.
"While this only provides a snapshot, it is an interesting insight that will help inform future policy. We will keep further deterrent measures under consideration."
A survey commissioned by ministers in Northern Ireland last year suggested 1% of drivers were using a mobile. There has been no similar research in Wales.