A Jewish reporter has been physically assaulted by a Republican Congressional candidate in Montana, with bystanders describing how the journalist was “grabbed by the neck with both hands and slammed into the ground”.

Ben Jacobs, a political reporter for the Guardian in the United States, was covering a special election for the state’s lone Congressional seat, which was left vacant when the incumbent, Ryan Zinke, resigned his position to become US Secretary of the Interior.

Although the seat has been held by a Republican for 20 years, there has been a tight electoral contest this time round between Greg Gianforte, the Republican candidate, and Rob Quist, his Democratic opponent.

Mr Jacobs approached Mr Gianforte at an event in the city of Bozeman, to ask him about healthcare policy.

In an audio recording of the incident, the reporter can be heard asking the candidate a question, to which the politician responds, “OK, speak with Shane, please”.

Immediately afterwards there are loud crashing sounds, and the candidate can be heard yelling: “I’m sick and tired of you guys. The last guy who came in here, you did the same thing. Get the hell out of here”.

The reporter can be heard saying: “You just broke my glasses… you just body slammed me and broke my glasses… you want me to get the hell out of here, I’d like to call the police”.

Mr Gianforte was subsequently charged with assault by the local sheriff’s office.

The altercation took place in front of witnesses; several employees of Fox News. In a statement released by Alicia Acuna, one of the journalists present, she described how Mr Gianforte “grabbed Jacobs by the neck with both hands and slammed him into the ground behind him… [and] 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!

“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”.

A statement released by the campaign claimed that when Mr Jacobs had declined to lower his recording device after being asked, the candidate “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.”

This version of the story directly contradicts the eyewitness account, as well as the audio recording.

Three Montana newspapers which had previously backed Mr Gianforte have withdrawn their endorsements. The congressional election will take place today, and the results are due to be announced sometime in the early hours of Friday morning.