During 2021, cryptocurrency companies bombarded Londoners with a record number of advertisements on public transportation, fueling calls for a ban to prevent people from being lured into risky investments.

The increase in advertisements for crypto assets, which are unregulated in the UK, has raised concerns about the risk of addiction and financial harm, especially given the wild volatility of digital currencies such as bitcoin, which reached record highs last year before plummeting again.

It was also revealed that Transport for London (TfL) has not implemented the mayor’s promised ban on gambling advertisements, allowing the industry to ramp up its marketing activity in the meantime.

TfL services displayed 39,560 crypto advertisements from 13 firms in the six months between April and September 2021, according to records obtained by the Guardian under the Freedom of Information Act.

The trading platform eToro, floki – a “meme coin” named after Elon Musk’s dog – Crypto.com, and Luno Money, whose campaign telling people it was “time to buy” bitcoin was banned by the advertising regulator for being “irresponsible.”

The promotional campaign outperformed previous years, as advertisers capitalized on the popularity of smartphone trading apps and raised awareness of digital currencies such as bitcoin and ether.

Despite widespread working from home in 2020, the volume of crypto ads increased, with companies such as Luno Money and Coinfloor collectively purchasing 1,595 ads.

Prior to the recent surge, 2018 was the busiest year for crypto ads on TfL since data collection began in 2017.

Even so, 15,000 were shown in 12 months, compared to 39,560 after only six months in 2021, including promotions for relatively obscure companies such as Hex, Kraken, BOTS, and Puglife.

Since 2018, crypto companies have spent a total of £825,245 to advertise on TfL tube and train services. The organization does not keep track of bus spending.

A separate freedom of information request by the Guardian revealed that the crypto advertising push was mirrored by a significant increase in gambling ads, as Khan’s promise to ban gambling ads in April 2021 appeared to be stalled.

Online casinos and bookmakers spent £783,476 in 2018-19 to advertise on TfL services, followed by £1m the following year and £1.16m in 2020-21.

However, they spent £1.17 million in the first three months of the 2021-22 fiscal year. While the Euros football championship is likely to have contributed to some of the increase, spending was nearly six times higher than in 2018, the year of the previous World Cup.

Khan promised to ban gambling advertisements in his manifesto, which was released nearly nine months ago, but a spokesperson for the Mayor’s office said it had yet to be implemented.

Siân Berry, former co-leader of the Green Party and now a member of the London Assembly, urged Khan to go ahead with the ban and extend it to crypto advertisements. “Investment bubbles have always worked by dragging in more and more inexperienced suckers towards the end of the cycle. That’s the stage at which some of these projects may be at with all this public advertising,” she said.

According to a TfL spokesperson, all advertisements include a disclaimer stating that cryptocurrency is unregulated in the UK and that the value of investments may fall.

The transportation body is vetting ads before they run and is said to be refusing any that use language similar to those banned or investigated by the ASA. It has written to both the FCA and the ASA seeking clarification.

“eToro fully supports measures, including regulation, designed to protect and educate investors about crypto and other financial asset classes,” said Dan Moczulski, managing director of eToro UK.

When asked about the concerns raised about their advertising, several crypto firms responded, claiming that any risks were well communicated and were not unique to crypto assets. The ASA is investigating one of Floki’s advertisements, and he claims that banning crypto ads would be “censorship,” and that ads should be regulated and include disclaimers.

It also stated that cryptocurrency was “anything but a bubble” and that it would “change the world as we know it.” Bubbles, according to Kraken, “generally don’t last more than a decade” with a high degree of institutional adoption.

BOTS stated that all investments carry risk and that the 2008 financial crisis demonstrated that traditional finance was not without risk.