President Donald Trump has been complaining to friends and advisers that Fox News is not loyal enough to him, the Daily Beast reported on Tuesday.

According to the report, Trump is concerned that the Fox chief Rupert Murdoch's sons, who are taking more important leadership roles in his media empire, are liberals.

Trump has repeatedly expressed his frustration with Fox in recent months, tweeting earlier in July that Fox News "is changing fast, but they forgot the people who got them there!"

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President Donald Trump has been quizzing friends, advisers, and media allies about the loyalty of Fox News, once his favorite cable network, the Daily Beast reported on Tuesday.

Citing three sources who have spoken with the president about the subject recently, the outlet reported that it is very much on the president's mind.

The sources said Trump had repeatedly asked "What the hell is going on at Fox?" and remarked that he's "been good to them."

According to the report, Trump has expressed concern that the Fox owner Rupert Murdoch's sons, who are playing key roles running their aging father's media empire, are "very liberal" and has asked his allies at the network whether the younger Murdochs can be trusted.

He has also reportedly instructed senior aides to do more interviews with networks other than Fox News, which has previously enjoyed unparalleled access to senior members of the administration.

Trump on Fox News. Screenshot/Fox News

In March, Lachlan Murdoch, Rupert's eldest son, took over as CEO of the Fox Corporation, the parent company of Fox News, following the sale of 21st Century Fox to Disney.

An extensive investigation by The New York Times found that Lachlan favors championing the conservative nationalist positions of hosts like Tucker Carlson.

But Lachlan's younger brother, James Murdoch, a former Fox executive, has told friends he's embarrassed about Fox News' coverage and takes a more liberal political position than his brother or his father, The Times reported.

Trump's anger at Fox News might come as a surprise to many, given its frequent reports favorable to Trump. Star hosts including Carlson and Sean Hannity have acted as informal advisers to him.

But the president has recently publicly accused the network of bias against him.

"Watching @FoxNews weekend anchors is worse than watching low ratings Fake News @CNN," he tweeted earlier in July. The network was said to have provoked his ire by broadcasting live footage of soccer fans in a French bar chanting insults about him.

The president wrote that Fox News "is changing fast, but they forgot the people who got them there!"

Earlier this year, he lashed out at the network for hosting town halls with Democratic presidential candidates.