Jimi Hendrix biopic All Is By My Side has caused a backlash over scenes that show the iconic guitarist beating his girlfriend.

Kathy Etchingham, who was a big part of Hendrix's live during his first months in London in 1966, is seen battered and bruised after he attacks her with a phone.

She spent three years with him and insists no such moment took place – and that she was blanked by producers when she offered to help them with their story.

All Is By My Side, starring Outkast rapper Andre Benjamin, was shown at the Seattle International Film Festival this week – leading to an instant negative reaction from Hendrix biographer Charles R Cross.

He tells MyNorthwest: "I hated it. The most shocking thing is Jimi is shown beating a woman twice. That woman is named Kathy Etchingham – she says that no domestic violence like that ever happened.

"For the book I interviewed 325 people, from family members to band members to girlfriends. I never heard a story that is even close to that."

Cross says he's kept in touch with Etchingham. "I've talked to Kathy a number of times and she's extremely upset about the way she's portrayed in the movie. When you're presented as a victim of domestic violence that's potentially libellous in and of itself."

And he insists writer and director John Ridley, known for his work on 12 Years A Slave, has failed to accurately capture Hendrix's character.

"It's a portrait of somebody who is somewhat detached and has these naggy women who were telling him what to do," says Cross. "That was not at all the way that Hendrix was.

"What's interesting is, you've had warring in the Hendrix family for years, since Jimi died. This is one of the first things that has ever come out which everyone agrees that they hate. Everyone believes that this was not what Jimi was."

All Is By My Side was produced without any Hendrix music after his estate, run by sister Janie, refused to take part. It's set for UK release on August 8.