The broadcast regulator said its latest Online Nation report for April – the height of the Covid-19 lockdown in the UK – found adults spent an average of just over four hours a day online.
That figure is up from the 3.5 hours recorded in September last year.
Communications services such as TikTok and Zoom are seeing unprecedented growth as people searched out new ways to stay connected.
According to the report, UK visitors to video-sharing app TikTok have more than doubled – from 5.4 million in January to 12.9 million in April.
The proportion of UK adults online making video calls has also doubled during lockdown, with seven in ten people now using such services at least weekly.
This increase has been most noticeable among older internet users, with the proportion of over-65s making at least one video call a week jumping from 22 per cent in February to 61 per cent last month.
But Ofcom said the biggest increase was seen on video conferencing platform Zoom, which rose from 659,000 UK users in January to 13 million in April.
The video platform has been one of the most popular services globally during the pandemic, as millions looked for ways to work and study from home, as well as catch up with friends and family.
The report also highlighted a change in communication habits, with people moving away from established forms of communication, such as landline calls and SMS messages.
Instead platforms such as WhatsApp and Facebook Messenger have become more regularly used than text message or email.
Online voice calls on platforms such as WhatsApp are now nearly as popular as mobile phone calls.
Yih-Choung Teh, Ofcom’s director of strategy and research said: “Lockdown may leave a lasting digital legacy.
“Coronavirus has radically changed the way we live, work and communicate online, with millions of people using online video services for the first time.
“As the way we communicate evolves and people broaden their online horizons, our role is to help ensure that people have a positive experience, and that they’re safe and protected.”
But despite these increases, the report also highlights that concerns remain over online safety.
Some 87 per cent of adults said they had concerns over children using video-sharing websites and other apps.
Although trust in sites to remove illegal and harmful content has risen among UK adults, more than half (57 per cent) said they support greater regulation of such platforms.
However, this figure is down on 64 per cent who said so last year.