People investing in cryptocurrencies like bitcoin should be prepared to lose all their money, Britain's financial watchdog warned Thursday as it revealed surging interest in the volatile assets.

The Financial Conduct Authority said that 2.3 million British adults hold cryptoassets, up from 1.9 million last year. 

At the same time, 38 percent of crypto users regard the assets as a gamble, down from 47 percent last year), "while increasing numbers see them as either a complement or alternative to mainstream investments", the FCA added in a statement.

"The research highlights increased interest in cryptoassets among UK customers," noted Sheldon Mills, FCA executive director, consumers and competition.

But he warned: "If consumers invest in these types of products, they should be prepared to lose all their money." 

The main cryptocurrency bitcoin has seen huge volatility over the past year.

Having begun a surge in late 2019 to reach $20,000 last December, it went on to reach $65,000 in April.

Bitcoin has since tumbled to trade around $40,000.

"The UK's financial watchdog is on alert, sniffing out fresh danger after its research shows the number of people holding crypto assets has risen by more than a fifth in just a year," noted Susannah Streeter, senior investment and markets analyst at Hargreaves Lansdown.

"The twists and turns in the crypto world are far from over and fresh gyrations in value are expected," she added.