The speculation around bitcoin is the "very definition of a bubble," Credit Suisse Chief Executive Officer Tidjane Thiam said as the currency exceeded $7,000 for the first time.
Bankers are steering clear of bitcoin out of concern that criminals could use its anonymity to hide their activities, he said Thursday at a news conference in Zurich.
"Most banks in the current state of regulation have little or no appetite to get involved in a currency which has such anti-money-laundering challenges," he said.
"From what we can identify, the only reason today to buy or sell bitcoin is to make money, which is the very definition of speculation and the very definition of a bubble."
Other bankers have also expressed skepticism about the currency. JPMorgan Chase CEO Jamie Dimon has called bitcoin "a fraud" that will eventually blow up.
UBS Group AG Chairman Axel Weber said last month that bitcoin has no "intrinsic value" because it's not secured by underlying assets.