Former U.S. Federal Reserve Chairman Ben Bernanke told CNBC on Monday that he doesn't believe bitcoin (BTC) works as money, a store of value or digital gold.

"If bitcoin were a substitute for fiat money, you could use bitcoin to go buy your groceries," he said. "Nobody buys groceries with bitcoin because it’s too expensive and too inconvenient to do that." he added, noting how it would be impossible to price something like celery in bitcoin because there's too little stability in its value.

Occasionally known as "Helicopter Ben" for suggesting in 2002 that the Fed could simply drop money from helicopters to ward off deflationary conditions – a comment the cypherpunks who laid the groundwork for Bitcoin were no doubt well aware of – Bernanke addressed the digital gold case for bitcoin. "Gold has underlying use value," he argued. "You can use it to fill cavities. The underlying use value of a bitcoin is to do ransomware or something like that."

Turning to monetary policy, Bernanke, who was behind the original zero interest rate policy and quantitative easing, criticized the current Fed for not moving quickly enough to tighten monetary policy in the face of advancing inflation.

Under even a "benign scenario," Bernanke said he expects the economy to slow and unemployment to rise, even as inflation remains high. "You could call it stagflation," he said.