Jeffrey Robinson, best-selling author of a scathing bitcoin take-down, told CNBC on Friday that he believes buying bitcoin is gambling not investing.

"It's a bubble," Robinson said on "Squawk Alley." "It's a loaded roulette wheel. You're better off in Vegas. The food is better."

In his 2014 book "BitCon," he called bitcoin "pretend currency," and wrote very few people use or accept it.

Despite additional adoption of bitcoin as a payment method since then, Robinson repeated that sentiment, saying "nobody is using it."

Robinson, a prolific writer who made his mark as an investigative journalist, said the media was responsible for promoting bitcoin and other cryptocurrencies. "I blame this network for bringing on these snake oil salesmen who tell you what a great investment it is." He added: "It's not an investment. It's not a currency."

During the interview, CNBC hosts defended the network, saying it brings on individuals from all sides to share their perspectives.

Robinson remain unconvinced, saying there is only one side to the bitcoin story and it's all bad.

Investing in cryptocurrencies, Robinson contended, is akin to the so-called greater fool theory: No matter the quality of an asset there's always someone out there willing to pay more for it.

"There is no use for bitcoin," he said, urging the government to warn people about what he feels is the questionable nature of digital coins.

Bitcoin was trading above $11,000 on Friday after sharp sell-offs earlier in the week, which at one stage saw it almost cut in half from last month's all-time high above $19,000.

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