A year ago, hoax theories about the dangers of 5G had barely pierced the public’s consciousness, largely remaining confined to serious conspiracy theorists such as David Icke.

In recent weeks, baseless claims about risks associated with the next-generation mobile technology have gone mainstream. Claims linking 5G to the coronavirus pandemic have led to petrol bomb attacks on phone masts and rebuttals from the government.

Industry insiders and factchecking experts point to a perfect storm of conditions that have helped the theory – described as “dangerous nonsense” – to take hold.

They cite the rapid growth of neighbourhood social media groups, a failure by networks to promote scientific evidence about 5G, and a terrified population looking to make sense of a world turned upside down.

The government and mobile networks have been left scrambling as the some members of the public have turned on telecoms engineers and carried out arson attacks on masts that in many cases do not yet have 5G equipment, as the rollout has been so slow.

Tom Phillips, the editor of the factchecking organisation Full Fact, said it warned last summer about the growing prevalence of 5G health claims. But in recent weeks debunked claims about 5G had been transformed, potentially aided by the creation of new local Facebook and WhatsApp groups to help support neighbours during the pandemic. Google Trends data suggests British interest in 5G theories exploded in the final days of March, shortly after the lockdown was imposed.

Phillips said one of the difficulties in battling the various claims was that it is hard to pin down exactly what is being suggested. “We’ve seen theories that the virus is real but 5G is making it worse, we’ve seen theories that the symptoms are not the result of the virus but purely the result of 5G, and we’ve seen theories that there are no outbreaks at all but it’s all a hoax to cover up the installation of 5G,” he said.

A senior member of staff at one UK mobile network blamed the rapid spread of a map that purported to show an overlap between countries that had coronavirus cases and countries that had rolled out 5G. The map was not accurate on either measure.

Other viral claims emphasised other supposed coincidences. A popular claim that Wuhan was the first city in the world to receive 5G took hold. But Wuhan received 5G coverage in August 2019, almost 18 months after O2 launched its first London testbed for the technology on the Greenwich peninsula. Iran, meanwhile, has seen an incredibly high number of coronavirus cases despite not having any 5G coverage.

The International Commission on Non‐Ionizing Radiation Protection, which sets guidelines on the output of mobile masts, says there is not a single scientifically substantiated adverse health effect that can be attributed to a normal 5G installation.

“We know parts of the community are concerned about the safety of 5G,” Dr Eric van Rongen, the chair of the ICNIRP, told the Guardian. “The guidelines have been developed after a thorough review of all relevant scientific literature, scientific workshops and an extensive public consultation process.”

As social media interest in the topic grew, some less scrupulous news outlets latched on to it as a potential source of clicks. The press regulation campaign group Hacked Off has noted that the Daily Star published an article on 24 March – the day after Boris Johnson ordered Britons to stay inside – with the headline “Coronavirus: Fears 5G wifi networks could be acting as ‘accelerator’ for disease”. The story, labelled as an exclusive, relied entirely on quotes from non-scientists.

Celebrities who often have larger audiences on Twitter and Instagram than many mainstream news outlets also boosted the theory, although some have since backed down. After the Britain’s Got Talent judge Amanda Holden was mocked for tweeting a link to a petition about the theory, her representative told media outlets that she had accidentally shared the link and did not endorse conspiracy theories.

Facing pressure from the government and a showdown with ministers, Facebook announced on Monday that it would start to actively remove false claims that linked Covid-19 to 5G and could lead to physical harm. However, its policy on other scientifically unjustified claims about 5G remain unclear.

Users on one of the biggest anti-5G Facebook groups in the UK mix pictures of apparently burnt-out mobile phone equipment with anti-vaccine material and baseless claims that coronavirus wards on hospitals are empty.

One prominent anti-5G group in Bristol defended itself from critics by adopting the language of those who distrust mainstream media and scientific voices, claiming that rejecting authoritative voices was the only way to find what is really going on.

Direct action in the UK against telephone masts is nothing new. When 3G equipment was being installed across the country in the mid-2000s there was similar outbreaks of concern about supposed health risks, with some resorting to direct action.

A long-running protest campaign against a mobile phone mast in the North Yorkshire village of Sheriff Hutton, partly on health grounds, culminated in a mysterious incident in 2007 in which concrete was poured into the base station.

Similar claims have been made for decades about the impact of microwave ovens and home wifi connections.

Yet despite warnings that public fears about 5G were growing before the pandemic, networks did little large-scale outreach work to counter the concerns. “I think as an industry we could have been quicker and clearer about what 5G is,” one network insider said. “As in, it’s basically the same as 4G in terms of how it uses mobile spectrum. We tend to get a bit bogged down on the technology and miss the wider picture.”

Tom Phillips, the factchecking journalist, said it was always tough to convince people to change their minds on such topics once they had decided a theory was true. He also said people who believed the theories needed to be treated with compassion.

“It is not enough to try and stamp out the poor quality information, you do have to put good information in its place,” he said. “And as soon you try to provide information, you run the risk of becoming part of the conspiracy theory – ‘you would say that, wouldn’t you?’”