Rupert Murdoch said on Monday that Facebook and Google have made "scurrilous" news sources popular, and that the U.S. tech giants should pay publishers if they want "trusted" content.

"Facebook and Google have popularized scurrilous news sources through algorithms that are profitable for these platforms but inherently unreliable," the News Corp. chairman said in a statement.

"If Facebook wants to recognize 'trusted' publishers then it should pay those publishers a carriage fee similar to the model adopted by cable companies," Murdoch said.

The statement comes after Facebook said Friday it would survey its users about what news sources they trust, and tweak its ranking software to help promote more the credible ones.

In his own Facebook post last week, CEO Mark Zuckerberg said, "I've asked our product teams to make sure we prioritize news that is trustworthy, informative, and local. And we're starting next week with trusted sources."

Facebook and Google have been gobbling up an ever-larger chunk of the digital ad market. The two companies are expected to post combined sales of just over $185 billion in 2018, based on Wall Street estimates compiled by Thomson Reuters.

Murdoch says the two companies should pay to ensure their users get quality journalism.

"Recognition of a problem is one step on the pathway to cure, but the remedial measures that both companies have so far proposed are inadequate, commercially, socially and journalistically.

"There has been much discussion about subscription models but I have yet to see a proposal that truly recognizes the investment in and the social value of professional journalism. We will closely follow the latest shift in Facebook's strategy, and I have no doubt that Mark Zuckerberg is a sincere person, but there is still a serious lack of transparency that should concern publishers and those wary of political bias at these powerful platforms," Murdoch wrote.

News Corp. bought Facebook rival MySpace for $580 million in 2005 and sold it for $35 million six years later.