Ralph Nader is at it again. No, not running for president, but rather slamming Liberty Media CEO John Malone as Charter Communications signs a deal to buy Time Warner Cable in a $55 billion cash and stock deal.

"Let's put it this way," Nader said on CNBC's "Fast Money," "John Malone became a multibillionaire not by being known as a consumer advocate and a believer in competition. This is all about concentrating power in eventually three giant cable companies that will control the bulk of cable business in this country."

Malone controls about a quarter of Charter Communications through Liberty Broadband, which will back financing for the deal. According to Forbes in 2014, Malone's net worth hit $7.7 billion and is likely to grow with the solidification of this new cable deal.

"This is a typical John Malone maneuver; empire building, monopolization advancing, and buying your customer base instead of winning your customer base by better competition," said Nader.

And this isn't the first time that Nader has gone after Malone. Last year, he called Malone's below-market-value bid for full control of SiriusXM radio "ludicrous." He even called on billionaire investor Carl Icahn to take note in what he thought was an unfair deal. Ultimately, Malone pulled his bid.

This time, Nader didn't just blame Malone, but pointed to the failures of the FCC, saying that Chairman Tom Wheeler "showed his hand too early." Nader said that the $2 billion breakup fee that was a part of the bid was a clear signal that the lawyers for the deal and the Justice Department are on the same page ahead of any official approval."

"I don't see anything good for consumers on this one," said Nader.

Read MoreCharter-Time Warner deal: A lower cable bill?

A spokeswoman for Malone declined to comment.

The Charter Communications-Time Warner Cable deal was announced Tuesday, a month after Comcast abandoned a bid for TWC in the face of opposition by the FCC.

Disclosure: Comcast is the owner of NBCUniversal, the parent company of CNBC and CNBC.com.