Donald Trump Jr. believes that his father, President Donald Trump, is on course to lose the presidential election in November, according to a profile published by The New York Times Magazine.

A spokesman for Trump Jr. strenuously denied the suggestion.

The Times magazine cited a Republican activist said to be in regular contact with the president's eldest son, though it did not name them.

The activist described Trump Jr. as "the only person who thinks they're going to lose. He's like, 'We're losing, dude, and we're going to get really hurt when we lose.'"

According to the report, Trump Jr. believes that if his father loses against Democratic candidate Joe Biden, it will result in federal prosecutions of the president, his family and political allies.