Jeremy Grantham renewed his long-running criticism of bitcoin , predicting it will gradually fade into irrelevance over decades.
The co-founder of investment firm GMO and a longtime market commentator known for his calls on asset bubbles, said bitcoin is a "useless, speculative" asset without intrinsic value, speaking on CNBC's "Squawk Box" Friday. He also said bitcoin hasn't outperformed during a bull market and questioned its practical use.
"[Over] years and years, decades and decades, it will dwindle away, I suspect – not with a bang, but a whimper," he said. "It's not a stable form of value – it just halved … for no particular reason in a strong economy, so you can't depend on it in that way."
He added that gold has still delivered solid gains over the same period, even after pulling back from its highs.
Bitcoin not only hasn't proved itself as a useful asset to speculate on, it doesn't provide any real world utility either, Grantham argued.
"People don't use it to make serious trades, they don't use it to buy their dinner and pay at the supermarket. … What it does is allows crooks to move money around," he said.
Bitcoin has become notorious over the years for its dramatic bear market crashes, which has taken it down at least 70% from its peak in every cycle. It's currently sitting about 52% off of its October peak, hovering below $60,000, and many investors believe the current price slump could drag on for several more months.