The communications watchdog said 33% of Britons opted for smartphones as the device of choice in 2014, ahead of 30% who preferred laptops.
Ofcom said the toppling of the laptop was a “landmark moment”.
Data from studies in 2014 also suggests that Britons took 1.2bn selfies last year, it said.
Some 31% of Britons said they had taken a picture of themselves in the past year, with one in 10 adults taking at least one per week, Ofcom added.
Backing up pictures
It said that the rise in smartphones with increasingly good cameras was potentially fuelling the craze.
The smartphone was found to be more popular than the digital camera for taking and storing photos in 2014, with 60% of adults and 89% of 16 to 24 year olds using their phone for photography.
However, just 29% of adults aged over 35 said they backed up their digital pictures, and 70% said they displayed printed copies of their favourites at home.
Ofcom compiles its Communications Market Report every year to monitor the UK’s habits.