Julian Assange's mother has hung up the phone on a Melbourne radio host after he taunted her with a Nazi slogan when she backed out of an interview.

Christine Assange was due to speak to 3AW's Sunday morning show about her son, the founder of whistleblower website WikiLeaks, and his successful appeal for asylum in Ecuador.

But she changed her mind after hearing how co-host John-Michael Howson had treated a previous guest.

"I won't be doing an interview with you because you're acting like a pig," Ms Assange said.

Howson responded by screaming on air: "Sieg Heil! Sieg Heil! Sieg Heil!"

Ms Assange then hung up the phone.

Howson said he linked Ms Assange to the biggest example of censorship that he could think of because she had denied him the chance to speak out.

"She comes on and says to me she's not going to talk about - that to me shows her trying to censor me," the veteran entertainment reporter said.

"I'm not going to be censored by her so I said, 'Sieg Heil! Sieg Heil!' because it's a Nazi mentality by these people."

Callers were divided on the appropriateness of his outburst.

Some said it was a disgusting way to treat a female guest, but the show's co-host Nick McCallum noted that Howson was an "equal opportunity abuser".

Last year Howson sparked outrage after verbally abusing his radio producer and co-host on air.

- AAP