Mr Carney said it was not clear the extent to which cryptocurrencies would ever become effective media of exchange.
He said: "Currently, no major high street or online retailer accepts Bitcoin as payment in the UK, and only a handful of the top 500 US online retailers do. For those who can find someone willing to accept payment for goods and services in cryptocurrencies, the speed and cost of the transaction varies but it is generally slower and more expensive than payments in sterling.
"That’s because the more heavily used cryptocurrencies face severe capacity constraints.
"For example, Visa can process up to 65,000 transactions per second globally against just 7 per second for Bitcoin. And if you use a debit or credit card in the UK, the transaction is completed in seconds and without exchange rate risk. In contrast, Bitcoin users can face queues of hours."
In September the rapid rise in bitcoin's value led the vice-president of the European Central Bank Vitor Constancio to compare it to the "tulipmania" of the 17th century, generally considered the first speculative bubble.
Meanwhile Jamie Dimon, chief executive of JP Morgan has called the virtual currency a fraud and said those who invest in it were "stupid".
Richard Turnill, global chief investment strategist at BlackRock said bitcoin could become mainstream in future years, but it is a long way from that point right now.
David Scott, an adviser at Andrews Gwynne in Leeds, said if equity markets are viewed as being in a bubble because the valuations bare no relation to the cash flow generated by the companies, then bitcoin must be an extreme case because it has no cashflow to back it up.