The economist who predicted the 2008 financial crash has warned American politicians that Bitcoin is "the mother of all scams" during a US Senate hearing on cryptocurrency.
Nouriel Roubini, a fierce critic of virtual currency who is known as Dr Doom for his bearish stances, took aim at the blockchain technology underpinning cryptocurrency.
It is often hailed as transformative, even by those cynical about digital coins.
"Blockchain is the most over-hyped technology ever," the New York University professor told the Senate banking committee.
"It is nothing better than a glorified spreadsheet or database. It is clear by now that Bitcoin and other cryptocurrencies represent the mother of all bubbles," he added.