In a speech for the Cambridge International Symposium on Economic Crime, FCA chair Charles Randell highlighted the risks of investing in the technology, particularly new coins backed by celebrities.
Randell was worried her fans could lose a fortune in the cryptobubble because they have little understanding of the risks associated with cryptocurrencies to purchase due to the "powerful fear of missing out".
It is a big deal in the US where people actually vote for reality TV stars, but Randal warned there were no shortage of stories of people who have lost savings by being lured into the cryptobubble with delusions of quick riches, sometimes after listening to their favourite influencers, ready to betray their fans' trust for a fee.
Kardashian West (pictured), whose idea of financial security is to wear mirrored glasses when playing poker, disclosed her social media post was an advert, as she was required to do by Instagram, but there was nothing to indicate how new the token was.
"She didn't have to disclose that ethereum max - not to be confused with ethereum - was a speculative digital token created a month before by unknown developers - one of hundreds of such tokens that fill the crypto-exchanges", Randell continued.
Ethereum is the second most popular cryptocurrency behind bitcoin but, beyond the similar name, there is no connection between it and ethereum max.
"Of course, I can't say whether this particular token is a scam. But social media influencers are routinely paid by scammers to help them pump and dump new tokens on the back of pure speculation. Some influencers promote coins that turn out simply not to exist at all."
It's been previously reported that Kardashian West's fee for social media adverts generally runs between US$300,000 to US$500,000 with a potential to reach US$1 million.
In the post, she asked if her followers were into crypto, saying "this is not financial advice but sharing what my friends just told me about the ethereum max token!"
She then invited them to swipe up "to join the e-max community".
The FCA says cryptocurrencies aren't regulated so anyone investing isn't covered by the Financial Services Compensation Scheme so people should be prepared to lose all their money. Ethereum max, which was also promoted by former NBA star Paul Pierce and boxer Floyd Mayweather, briefly spiked in popularity around the time it was being advertised by the influencers.
At its peak each max coin was worth US$0.000000597636 but since then has lost over 95 percent of its value and is now trading at just US$0.000000027158, according to CoinGecko.