The Republican candidate in a crucial US election race has been charged with assault after he allegedly "body slammed" a journalist.

The Guardian posted audio of the altercation between Greg Gianforte and their reporter Ben Jacobs, who had been trying to ask the tech millionaire questions about Donald Trump's controversial healthcare plan.

Banging and crashing sounds are heard on the tape before the candidate shouts "Get the hell out of here" at the US-based political reporter.

Mr Jacobs later tweeted: "Greg Gianforte just body slammed me and broke my glasses."

The incident was witnessed by a Fox News crew who had been preparing to interview the congressional candidate in Montana's special election - which is regarded as a referendum on the Trump presidency.


Greg Gianforte just body slammed me and broke my glasses — Ben Jacobs (@Bencjacobs) May 24, 2017

Fox reporter Alicia Acuna said Mr Jacobs had entered the room as they were setting up, put his voice recorder up to Mr Gianforte's face and asked about the latest developments on the American Health Care Act.

She wrote: "Gianforte told him he would get to him later. Jacobs persisted with his question. Gianforte told him to talk to his press guy, Shane Scanlon.

"At that point, Gianforte grabbed Jacobs by the neck with both hands and slammed him into the ground behind him.

"Faith, Keith and I watched in disbelief as Gianforte then began punching the reporter. As Gianforte moved on top of Jacobs, he began yelling something to the effect of, 'I'm sick and tired of this!'

"Jacobs scrambled to his knees and said something about his glasses being broken. He asked Faith, Keith and myself for our names. In shock, we did not answer.

Image: Rob Quist has won high profile backing from Bernie Sanders

"Jacobs then said he wanted the police called and went to leave. Gianforte looked at the three of us and repeatedly apologised. At that point, I told him and Scanlon, who was now present, that we needed a moment. The men then left.

"To be clear, at no point did any of us who witnessed this assault see Jacobs show any form of physical aggression toward Gianforte, who left the area after giving statements to local sheriff's deputies."

Mr Gianforte's spokesman Shane Scanlon provided a conflicting account, saying Mr Jacobs "entered the office without permission, aggressively shoved a recorder in Greg's face, and began asking badgering questions".

He added: "After asking Jacobs to lower the recorder, Jacobs declined. Greg then attempted to grab the phone that was pushed in his face.

"Jacobs grabbed Greg's wrist, and spun away from Greg, pushing them both to the ground. It's unfortunate that this aggressive behaviour from a liberal journalist created this scene at our campaign volunteer BBQ."

Image: Folk singer Mr Quist performs with his daughter Halladay

Mr Jacobs reported the incident to the police, who said they had completed their investigation and Gianforte had been issued with a charge of misdemeanour assault.

Gallantin county sheriff Brian Gootkin said in a statement: "Following multiple interviews and an investigation by the Gallatin county sheriff's office it was determined there was probable cause to issue a citation to Greg Gianforte for misdemeanor assault.

"The nature of the injuries did not meet the statutory elements of felony assault. Greg Gianforte received a citation on Wednesday night and is scheduled to appear in Gallatin county justice court between now and 7 June, 2017."

In a later statement, the sheriff acknowledged he had donated £193 ($250) to Mr Gianforte's campaign in March but said that had "nothing to do with our investigation, which is now complete".

The election called when Interior Secretary Ryan Vinke vacated his seat in March has attracted national attention and spending of more than £13.1m ($17m).

Mr Gianforte's Democratic opponent is folk singer Rob Quist, who has taken aim at the President's healthcare plan, which he calls a "tax cut for millionaires".

Mr Quist declined to comment on the alleged attack when approached by reporters on Wednesday.