A web page and a Facebook post by Arsenal football club promoting crypto-based fan tokens broke advertising rules, a watchdog has ruled.
The Advertising Standards Authority (ASA) argued the club had "failed to illustrate the risk of the investment".
It ruled "the ads must not appear again in the form complained about".
Arsenal said it would seek an independent review of the ruling, adding that the club had provided information on the financial risks.
Several top-tier football clubs offer fan tokens.
But critics, including some supporters' groups, suggest that clubs who promote crypto fan tokens are encouraging people to engage in the risky, and largely unregulated, world of cryptocurrency investment.