Unfounded theories linking Covid-19 to 5G technology are the most common example of online misinformation in the UK, an Ofcom survey suggests.
The media regulator said 50% of respondents had seen some examples of misinformation during the third week of lockdown - up from 46% in week one.
Of those, half had seen the disproven 5G conspiracy theory, it said.
There are concerns the false claims prompted people to set communication masts set on fire across the UK.
A spokesman for industry body Mobile UK told BBC News there had been "more than 50" of these arson attacks but fewer in recent days.
Claims 5G spreads coronavirus or weakens people’s immune systems, making them susceptible to it, have been denounced as "compete rubbish" by scientists.
“From my own experience, [the survey] does reflect reality,” cyber-security expert Graham Cluley said.
"A lot of people are talking about it and a worrying number of people seem to be giving it some kind of credence."
He added he worried there would be a flood of anti-vaccination conspiracy theories if and when a vaccine for coronavirus was made available.
The proportion of those surveyed using a fact-checking website rose from 10% in the first week of the lockdown to 18% the week after, dipping to 15% in week three.
And the proportion saying they were finding it hard to determine what was true online fell from 40% to 32%.
Meanwhile, 97% continued to access news about Covid-19 at least once per day.
Although, 39% of the 25- to 34-year-olds, up from 30% in the first week, said they were trying to avoid it.
More of the respondents (33%) chose the BBC as the most important source of news and information during the pandemic than any other provider.