On an already busy Wednesday that featured not only a series of critical earnings reports but the long-awaited Congressional testimony of Special Counsel Robert Mueller, Treasury Secretary Steven Mnuchin returned to CNBC for the second time in a week to offer an update on trade talks with China.

But his comments on China were hardly the most interesting thing the Treasury Secretary said on Wednesday: He also offered perhaps his harshest criticism of Amazon yet.

"There’s no question they’ve limited competition," Mnuchin said. "If you look at Amazon, although there are certain benefits to it, it destroyed the retail industry across the United States, so there’s no question they’ve limited competition."

He added that the DOJ was "absolutely right" to look into antitrust issues involving US tech firms.

Mnuchin's remarks came less than a day after the latest update on the DOJ's efforts to hold America's largest tech firms responsible for anti-competitive practices.

Weighing in on Peter Thiel's accusation that Google should be investigated for treason over its work with the Chinese government (which was taking place as the company severed its ties with the DoD over pressure from its employees, Mnuchin said he was

"not aware of Google working with the Chinese govt in any way that raises concerns."

The interview later returned to the subject of cryptocurrencies (the focus of Mnuchin's last interview with CNBC). Mnuchin joked that he wouldn't be investing in bitcoin any time soon.

"I can assure you I will personally not be loaded up on bitcoin" in 10 years, says Treasury Secretary Mnuchin #bitcoin pic.twitter.com/0J5acWQwRO — Squawk Box (@SquawkCNBC) July 24, 2019

We imagine we'll be hearing more from the Secretary in the coming days as he prepares to head to Beijing for the next round of talks with his Chinese counterparts.

Watch the full interview below:

Watch Treasury Secretary Mnuchin's full interview on trade, Big Tech and more from CNBC.