Malcolm Turnbull's overthrow of Tony Abbott has "set off a civil war within News Corp", according to one of the publisher's most popular and conservative commentators, Andrew Bolt.

Mr Bolt claimed The Australian was probably losing $20 million a year and was being subsidised by the tabloids he writes for, including the Herald Sun and the Daily Telegraph.

In a personal attack during his regular 2GB radio show with Steve Price, Mr Bolt said The Australian's editor-in-chief Chris Mitchell had acted unprofessionally by pursuing "personal vendettas" against him.

"He called it off a couple of days before [News Corp chairman] Rupert Murdoch came to town [in August]. Now that Rupert Murdoch is away, back in America, it seems to be on again," Mr Bolt told Mr Price on Monday night.