The American stockbroker immortalised in the film The Wolf of Wall Street has warned that the craze for initial coin offerings has become "the biggest scam ever".

Jordan Belfort said ICOs, a new fundraising method linked to cryptocurrencies like bitcoin, are "far worse than anything I was ever doing".

Mr Belfort, who was played by Leonardo DiCaprio in the 2013 film, spent 22 months in prison for crimes including fraud after running scams that cost investors around $200m (£150m). Since leaving prison he has earned millions as a motivational speaker and author.

ICOs involve a company issuing cryptographic tokens, usually in exchange for a cryptocurrency like bitcoin or ether, as an alternative to selling shares or raising debt. Those cryptographic tokens can then be separately traded, or exchanged for services from the company itself.

Over $2bn was raised in ICOs in the first nine months of 2017, according to CB Insights, compared to just $54m in the same period last year. This year bitcoin has risen from under $1,000 to over $6,000.