NAB has never banked or traded in digital currencies, but has provided banking services to companies who do.

Confirming the move, a spokesman said: "NAB continually reviews its risk profile and the businesses we bank, ensuring NAB's activities are in the best interest of our customers and our shareholders."

The decision follows recent moves by the Bank of Ireland and the Bank of Montreal to distance themselves from customers who trade in digital currencies.

It also comes a month after Japanese bank Mizhuo was named in US and Canadian lawsuits brought against the bankrupt Mt. Gox exchange, for which it provided banking services.

Mt. Gox, the world's biggest exchange, announced in February it had been robbed of all its bitcoins in a massive cyber attack.