The Facebook and website posts included a video featuring Gunners players Ben White, Calum Chambers and Kieran Tierney and read: ‘Fans should be aware that they could lose some or all of their money invested. We advise you to spend only what you can afford and seek independent financial advice if required.’

The Advertising Standards Authority (ASA) investigated whether the adverts took advantage of consumers’ inexperience or credulity and trivialised investment in cryptoassets, failed to illustrate the risk of the investment and did not make clear the “token” was a cryptoasset, which could only be obtained by opening an account and exchanging with another cryptocurrency.

Arsenal said fan tokens were used to encourage fan participation and were different to cryptocurrencies, which were virtual currencies used as a means of payment.

The club said it promoted the tokens responsibly by reminding fans they only needed one token to vote in decisions, that they should only purchase what they could afford and urged buyers to seek independent financial advice if required.

The ASA said the Financial Conduct Authority categorised utility tokens as cryptoassets, which were a complex and sophisticated investment, subject to frequent change in value and one that could potentially lead to large losses.

The watchdog said: ‘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.

‘We therefore considered the potential tax implications were not made sufficiently clear to consumers considering investing in it.’

The ASA concluded: ‘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.”

A spokesperson from Socios, which partnered with Arsenal in July to launch the club’s fan tokens, added: “We welcome Arsenal’s call for an independent review. This is a fast-moving area and clarity is needed to ensure all companies can adhere to the latest guidelines.”