Unregulated online forums give anti-vaccination “quacks and cowboys” a free hand to peddle conspiracy theories and market dodgy “miracle cures”, a new study has found.

Campaigning Labour MP Lucy Powell is calling on the government to act after she uncovered that so-called anti-vaxx groups on Facebook now have more than 800,000 members.

Where information is public, her team found UK-based moderators peddling dangerous myths about “establishment cover-ups” and dodgy “scientific studies” claiming vaccinated children were more likely to suffer from hayfever, eczema, learning disabilities, ADHD, autism and chronic illness.

At least 12 of the hidden forums, which have 130,000 members, have UK administrators, underlining the prevalence of the anti-vaxx movement in Britain. 

One page was pushing “alternative” medicines and “miracle” cancer “cures” sold by a Welsh business and promoting UK-made documentaries about the anti-vaxx movement. 

It comes as Public Health England (PHE) said this week that as many as one in seven five-year-olds starting school this September may not have had both MMR (mumps, measles and rubella) vaccine doses. A further 30,000 have not yet received either dose of the vital vaccine. 

This week Britain lost the ‘measles-free’ status awarded by the World Health Organisation (WHO) – three years after the virus was eliminated in the country.

The PHE figures suggest overall that 87% of children have had both doses of the MMR vaccine against measles, mumps and rubella, compared with the target of 95%.

Powell, the Labour MP for Manchester Central, said the rapid spread of anti-vaxx misinformation online means it is “simply not enough for the PM to say parents shouldn’t listen to superstitious mumbo jumbo”.

UK administrators were from a spread of locations, including Brighton, Edinburgh, Sheffield and London. 

A quick audit of the few anti-vaxx posts that are public today uncovered administrators making false claims about Prime Minister Boris Johnson’s plea for parents to ensure their children were vaccinated against measles. 

Powell said Johnson and Health Secretary Matt Hancock MP must hidden online spaces which promote anti-vaxx myths if they are serious about reversing declining immunisation trends.

“We need ministers to go after these quacks and cowboys online,” she told HuffPost UK. “Online forums are misinforming quite normally concerned parents, putting children in harm’s way.

“The fake news and scare stories which spread across the internet via these Facebook groups are the root cause of the worryingly low rates of immunisation we see in Britain today against illnesses like measles.” 

Powell is attempting to change the law via her Online Forums Bill so government can target hidden social media echo chambers that allow the spread of hate speech, fake news and radicalisation. 

Her bill, which won the support of Jacob Rees Mogg and Nicky Morgan before they took up ministerial roles in Johnson’s new government, would make moderators responsible for hate speech or defamation and remove their right to anonymity. The legislation would also force platforms to publish information about secret groups.

Bill Gates, whose foundation is investing billions in vaccinations worldwide, is at the centre of one of the most prominent anti-vaxx conspiracy theories, Powell said. Some UK forums falsely claim Gates promotes vaccines in order to “depopulate the earth”, that he has huge financial interests with pharmaceutical companies and hasn’t vaccinated his own children. 

Powell’s research had shown anti-vaxx scammers were able to “profit from parents’ fear and naivety” by selling fake products, said Powell. 

“The groups we found are just the ones operating in the open,” she said. “We have no way of knowing how many secret groups exist in which similar or worse misinformation is being pumped into parents’ newsfeeds. Only Facebook can access that information. 

“The government must act to regulate these spaces to put an end to the harm they cause. They must ban large forums from being completely secret, which currently locks out charities and the police, and make the administrators who are peddling dangerous lies for their own financial gain legally liable for their actions.”  

The prime minister is preparing to host a summit with social media companies and has urged firms to do more to tackle anti-vaxx fake news on their platforms.