"I like bitcoin" and the security of the blockchain ledger technology behind cryptocurrencies, the California Republican said, as he criticized Facebook's plans for a Libra digital coin ahead of hearings on Capitol Hill this week.
Libra will be pegged to a basket of government-backed money, compared with bitcoin, which is highly volatile in price and derives value from factors including its ability to enable instantaneous, anonymous, global payments and as an investment.
Nobody controls bitcoin.
McCarthy did, however, say that bitcoin is not where it needs to be yet, alluding to the risks of cryptocurrencies being used by criminals and money launderers.
While Libra promises more stability, McCarthy remains concerned.
"When I'm on Facebook, I'm not the customer, I'm the product," he said. "Facebook is free because they sell your data to make money. Now they want to get into the business, and they're not bitcoin, in this Libra. They're not decentralized."
In Libra hearings by the Senate Banking Committee on Tuesday and House Financial Services on Wednesday, McCarthy said he's looking for the social media giant to address its potential anti-competitive behavior.
"I want to see decentralization because Libra concerns me that they're going to control the market," McCarthy said.
To address those concerns, Facebook set up Libra to be run by a nonprofit consortium supported by a range of firms and organizations, including including payment companies Visa and PayPal, as well as tech giants eBay, Lyft, Spotify and Uber.
Republican Sen. Pat Toomey strayed from McCarthy's and the Trump administration's critical views o Libra, telling CNBC in a separate interview Tuesday that Facebook's planned digital coin should be given a chance.
"I don't want to presume in advance that we've got to prevent the development of some new innovation," Toomey offered.
However, the Pennsylvania senator added he wants to know the real motivation behind Libra because Facebook has said that it's not about making money.