A US federal judge has thrown out Donald Trump's £370m ($475m) defamation lawsuit against CNN.

The former US president had claimed the network's description of his 2020 election fraud claims as the "big lie" associated him with Adolf Hitler. The phrase is associated with the Nazi regime's use of propaganda.

In a lawsuit filed in October 2022, Trump’s legal team claimed CNN had defamed Trump after its on-air pundits repeatedly compared his false election fraud claims to the way Hitler used propaganda in his own rise to power. 

It highlighted five instances in which CNN either published stories or aired comments referring to Trump's assertions about the 2020 election as his "big lie." 

Trump’s lawyers explained in their lawsuit: “The ‘Big Lie’ was used by Hitler to incite hatred of the Jews and to convince people to ostracise Jewish people.

“It was an entire propaganda campaign to justify Jewish persecution and genocide. The phrase is not taken lightly and is not bandied about blithely. CNN anchors and commentators understand this. 

“They have not used it against other political leaders and previously criticised political analogies to Nazi Germany and to Hitler.”

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Donald Trump enters Erie Insurance Arena for a political rally while campaigning for the GOP nomination on Sunday (Photo: Getty)

But in a ruling, US Judge Raag Singhal said CNN's words were opinion, not fact, and therefore could not be the subject of a defamation claim.

The judge, who sits in federal court in Fort Lauderdale, Florida, wrote: "CNN's statements while repugnant, were not, as a matter of law, defamatory.”

The mere use of the phrase "big lie" is not enough to give rise to a true connotation, Singhal added.

A Trump spokesperson said: "We agree with the highly respected judge's findings that CNN's statements about President Trump are repugnant. 

“CNN will be held responsible for their wrongful mistreatment of President Trump and his supporters."

The statement did not say whether Trump would appeal the decision.

Since launching his first presidential campaign in 2015, Trump has often attacked media outlets whose coverage he dislikes, with CNN a favourite target.

Trump had a tense relationship with CNN during his White House term, branding the broadcaster "fake news" and repeatedly raging against them on social media.

Trump is the front-runner for the 2024 Republican presidential nomination, despite facing both state and federal indictments.