Fraudsters are using celebrities' names to add a touch of legitimacy to cryptocurrency scams.
Dargon's Den star Deborah Meaden and MoneySavingExpert.com founder Martin Lewis are among the fake endorsements used by scammers to extort £34,000 from victims last month alone.
Action Fraud said that it received 21 reports of cryptocurrency scams in March, and warned that online advertising is tricking people into investing.
“Opportunistic fraudsters are taking advantage of this market, offering investments in cryptocurrencies and doing everything they can to defraud unsuspecting victims," said Pauline Smith, director of Action Fraud.
“Anyone who invests in cryptocurrencies should thoroughly research the company they are choosing to invest with."
Fake quotes from prominent individuals often appear on the websites for the scams, encouraging investors to put money into cryptocurrencies.
“With the growing sophistication of online fraud, it becomes increasingly important to carry out checks before parting with cash online," said Deborah Meaden. "A quick Google search will often reveal the truth and all online advertising should be read set against the premise of “If it looks too good to be true then it probably is!”
Money man Martin Lewis said he found it "sickening" that fraudsters were "leeching off" the trust of his audience.
“Let me be very plain. I never do adverts. If you see my picture in an advert on Facebook or anywhere else recommending products – be it Bitcoin, binary trading, PPI firms or anything else – they are nothing to do with me. Be very, very careful.”
The warning comes after technology giants Google, Facebook and Twitter all announced measures to crack down on cryptocurrency adverts on their platforms, due to rising concerns that some are fraudulent.