The value of bitcoin has fallen from $19,850 in December to $6,575 after the value of the cryptocurrency halved in less than two months.
Banks are concerned customers will run up huge debts due to the volatility of cryptocurrencies.
It is thought hundreds of thousands of people invested in bitcoin last year as the digital currency’s value soared in the final months of 2017.
Bitcoin value reached $19,600 in December, before rapidly falling to less than $6,000 today.
The news comes amid growing international concerns about how the increasingly popular cryptocurrencies are being used, with fears some people are using them to launder money.
Greg Adams, the managing director of blokt.com, told Express.co.uk the law surrounding cryptocurrency is in desperate need of further clarification.
He said: “The banks are likely feeling the heat right now; they have customers that used debt to enter the market during the recent Bitcoin bull run.
“Customers that entered at the top (close to $20,000) using a credit card will be panicking seeing their investments down over 60 per cent.
“The law regarding buying cryptocurrency on credit is a grey area and is in need of clarity. Banks are probably worried about being liable for losses.
Theresa May has previously earned about the dangers of cryptocurrencies and said it is something that should be looked at “very seriously”.
She said: “Cryptocurrencies like bitcoin, we should be looking at these very seriously, precisely because of the way that they can be used, particularly by criminals.”
Cryptocurrency technology allows users to make payments and store money on the internet without needing to use their name or a bank.
The Treasury said that it intends to update regulation to bring virtual currency platforms into anti-money laundering and counter-terrorist financing regulation.
Facebook recently announced it would block any advertising that promotes crypto-currency products and services.