In a statement obtained by Michael D. Shear of The New York Times' The Caucus, the organization says it plans to use the money to intensify its efforts to hold the Fox host Glenn Beck and others on the cable news channel accountable for their reporting.
"Fox has transformed itself into a 24-7 G.O.P. attack machine, dividing Americans through fear-mongering and falsehoods and undermining the legitimacy of our government for partisan political ends," the group will say in the statement, to be released Wednesday afternoon.
In an accompanying statement, Mr. Soros, a billionaire who has a history of supporting liberal politicians and causes, accused Fox News hosts of "incendiary rhetoric" and said he hoped that his money would be used "in an effort to more widely publicize the challenge Fox News poses to civil and informed discourse in our democracy."
For years, conservatives have accused Media Matters of being a front organization for Mr. Soros. In May, Mr. Beck referred to Media Matters as "the left-wing George Soros-funded media machine that is now referring to me as a jihadist." In 2007, Fox's Sean Hannity called it "Hillary Clinton's George Soros-funded group Media Matters."
Officials at Media Matters regularly deny that they have ever taken money from Mr. Soros, who repeats that denial in Wednesday's statement, saying, "I have not to date been a funder" of the liberal organization. Now, he will officially be a donor, and likely a fresh target for criticism from the right.