Posts by Premier League club Arsenal promoting fan tokens broke advertising rules, a watchdog has ruled.

The British Advertising Standards Authority (ASA) said Arsenal had taken "advantage of consumers' inexperience" in cryptoassets.

The posts, which appeared on Arsenal's Facebook page and website and featured three first team players in Ben White, Kieran Tierney and Calum Chambers, were promoting the club's partnership with fan tokens company Socios.

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Arsenal said the cryptocurrency-based fan tokens were intended to increase fan engagement by allowing holders exclusive votes in minor club issues. Premier League champions Manchester City and Italian club AC Milan have also launched fan tokens this year.

Fan tokens can be traded on digital exchanges and, like other cryptoassets such as bitcoin and NFTs (non-fungible tokens), have a tendency for wild price swings, leading some regulators to issue warnings to investors.

In their posts, Arsenal reminded fans they could lose some or all of their money invested in the product and that they should only spend what they could afford.

In its ruling, the ASA stated: "We acknowledged that the ads did not promote the fan tokens as an investment or financial product.

"However, the product was a cryptoasset regardless of how it was promoted and the ads did not contain any information that Capital Gains Tax (CGT) could be payable on profits from investing in cryptoassets.

"Therefore, because the ads trivialised investment in cryptoassets and took advantage of consumers' inexperience or credulity by not making clear that CGT could be payable on profits from investing, we concluded the ads were irresponsible and breached the Code."

An Arsenal spokesman said: "We take our responsibilities with regard to marketing to our fans very seriously. We carefully considered the communications to fans regarding our promotions and provided information regarding financial risks.

"We will endeavour to comply with the ASA's guidance regarding future communications in this fast moving area, however we will be seeking an Independent Review of the ASA's ruling to seek greater clarity on the ASA's current position."