The notice tells these firms to review their ads and to ensure they understand and are complying with the rules "so that consumers are treated fairly".

Specifically, ads must clearly state that cryptocurrencies are unregulated in the UK and that the value of investments are variable. They must also not imply that investment decisions are "trivial, simple, easy or suitable for anyone" or "imply a sense of urgency to buy or create a fear of missing out".

The ASA has already recently banned several crypto ads for misleading consumers and being "socially irresponsible".

The watchdog says it will continue to monitor for compliance and implement sanctions if it does not see improvements.

It is also working with the FCA, which itself recently revealed it opened over 300 cases related to crypto firms in a six-month period last year and has 50 live investigations, including criminal probes, into companies in the sector.

Separately, the Central Bank of Ireland has issued a fresh warning about the risks of investing in crypto assets, as part of a European-wide campaign by the European Supervisory Authorities.

The Central Bank again emphasised that crypto assets are highly risky and speculative, and that people need to be alert to the risks of misleading advertisements, particularly on social media, where influencers are being paid to advertise crypto assets.

Derville Rowland, director general financial conduct says: “In Ireland and across the EU we are seeing increasing levels of advertising and aggressive promotion of crypto asset investments.

“While people may be attracted to these investments by the high returns advertised, the reality is that they carry significant risk.

“Before you buy crypto assets, you need to think about whether you can afford to lose all the money you invest. Do the promised fast or high returns seem too good to be true?”