Donald Trump has renewed his feud with the Fox News host Megyn Kelly.

Republican presidential frontrunner said Megyn Kelly, who returned to her show on August 24 after a break, “must have had a terrible vacation” because “she’s really off her game”.

Fox News chief Roger Ailes has demanded an apology, describing Donald Trump’s verbal attack as “disturbing”.

It comes two weeks after controversy over Donald Trump’s remarks about Megyn Kelly following the first Republican debate.

In a CNN interview, Donald Trump said the Fox presenter “had blood coming out of her eyes, blood coming out of her wherever” to describe the way she questioned him during the debate over comments he had made about women.

Donald Trump was subsequently dropped as a speaker at a major conservative forum, and his comment was denounced by rival Republican candidates.

But it did not stop him from continuing his verbal attack of Megyn Kelly during her show on August 24, tweeting: “Kelly File was much better without Megyn Kelly. Her replacement while she was out on vacation was much better!”

Fox News chairman Roger Ailes, who had cleared the air with Donald Trump after the debate, reacted strongly to the “surprise and unprovoked attack” on his news host. In a statement read aloud on the channel, he said it was “as unacceptable as it is disturbing”.

Megyn Kelly “represents the very best of American journalism and all of us at Fox News Channel reject the crude and irresponsible attempts to suggest otherwise,” he added, demanding an apology.

Some of Megyn Kelly’s colleagues also came to her defense, including Bret Baier, her co-host for the debate, who tweeted “this needs to stop”.

Donald Trump seemed unfazed by the criticism, saying he disagreed with Roger Ailes’ statement and that he did not consider Megyn Kelly “a quality journalist”.

Donald Trump has taken the lead in the polls ahead of the 16 other Republican candidates, despite a string of controversial remarks since launching his campaign.