(Reuters) - Tech and competition watchdog groups have called on the U.S. Department of Justice to probe YouTube, saying the video-streaming platform could enable Google and its parent company, Alphabet, to dominate home entertainment.

In a letter to Justice Department antitrust chief Jonathan Kanter dated Tuesday, the American Economic Liberties Project, Demand Progress and nine other groups expressed concern about YouTube's growth as a competitor to cable and streaming services and its pre-installation on smartphones and TVs sold in the U.S.

The groups called on the regulator to investigate YouTube, which is among the top streaming services in the U.S. Google already dominates the internet search market and is a leader in online advertising technology.

"YouTube has a decade-long record of using its dominance across numerous markets to crowd out competitors, lock in customers, and force the purchase of bundled services," the groups wrote.

The growth of YouTube TV, the company's subscription streaming service, increases Google's "prospects for living room dominance," the groups said.

"Anyone looking for something to watch can see this space is very competitive," said a YouTube spokesperson, adding that the company goes head to head with both streaming services such as Netflix ( NFLX ) and Disney+ and other video platforms like Meta's Instagram and TikTok.

In April, Alphabet reported YouTube quarterly ad revenue of more than $8 billion, up 21% from the same period last year.

Google executive Philipp Schindler said at the time that the platform had been the most-watched U.S. streaming service for more than a year, citing data from audience analytics firm Nielsen.

Google is already fighting two antitrust lawsuits brought by the Justice Department and several states. One claims the company monopolizes the online search market and another that it dominates the market for digital advertising technology.

Google has fought both cases, saying its successes came by lawful means. 

YouTube, according to the advocacy groups, is "the third leg of the stool that supports Google's monopoly."

Lee Hepner, a lawyer at the American Economic Liberties Project, compared the groups' concerns about YouTube to the conduct challenged in the search case, where antitrust enforcers have alleged that multibillion-dollar revenue sharing agreements with smartphone makers have allowed Google to maintain online search dominance.

"What is Google TV if not principally a distribution system for Google's own streaming service?" Hepner said.

Antitrust concerns over Big Tech have spanned administrations, with a case against Google and one against Facebook parent Meta Platforms filed under President Donald Trump's administration.

President Joe Biden's antitrust enforcers have followed with a second case against Google and cases against Amazon.com ( AMZN ) and Apple.