Brits are losing tens of millions of pounds a year to 'subscription frauds' - and are often lured in by celebrity endorsements that later turn out to be fake.
Around 300,000 people every year sign up to these frauds, which often pretend to be advertised by celebs like comedian Russell Brand, survivalist Bear Grylls and Dame Esther Rantzen.
Subscription frauds advertise products or services online, using famous faces to gain consumers' trust - but the celebs have
But the famous faces backing the products are often unaware they are being impersonated, according to the BBC Radio 4 programme File on 4.
Many of the frauds rely on Facebook adverts to target their victims.
File on 4 found more than 800 on the social network.
Facebook told the BBC it has removed almost all of the offending adverts, which break its rules.
The scams often also impersonate genuine news websites like MailOnline - and even The Mirror.
One woman, Louisa Dyson, 40, from Doncaster, was taken in by a fake MailOnline article with 'Russell Brand' advertising CBD gummies for pain relief.
CBD is a legal extract from the cannabis plant, which users say can give benefits like relaxation and pain relief but without any intoxication.
Louisa paid £38.99 for what she believed would be a 'buy one get one free' offer on the gummies, but was actually charged £148.
She ended up losing the money, though her bank blocked the scammers from taking any more cash.
Fraud investigator Gillian Schonrock told the BBC: "In the UK, there are in the region of 300,000 victims per year and they are losing on average around £250 - that puts it into the [region of a] £75million-a-year loss to UK victims.
"We're not talking here about the odd fraudster who has managed to set up one small scheme here, we're talking about thousands of scammers and huge amounts of money.
"On a global scale, we're talking $1billion (£0.7billion) a year or more."
Dame Esther Rantzen said: "I loathe them incorporating my name and therefore, if you like, my reputation to sell their products, which I know nothing about.
"It really is so anger making, now I feel helpless and I'm being conned myself."
MoneySavingExpert founder Martin Lewis is also commonly impersonated by scammers.
Last year Lewis told MPs how one woman lost £15,000 to scammers who were pretending to be him.
The consumer expert had previously issued High Court proceedings for defamation against Facebook after over 1,000 fraudulent adverts abusing his name or image had appeared on the site.
These adverts typically use his face to advertise fake financial products or scams, designed to con unsuspecting victims out of thousands of pounds.
Martin settled the lawsuit after Facebook agreed to donate £3million to an anti-scam charity. The social media site has also since launched a new scam ads reporting button.
