John Hewson says Tony Abbott was not always loyal

Much has been made of Tony Abbott's loyalty to his colleagues but he was also disloyal to others, former opposition leader John Hewson says.

Dr Hewson said Mr Abbott had stood by former speaker Bronwyn Bishop and his chief of staff Peta Credlin.

"I suffered from his disloyalty because he was a constant channel from my office to John Howard," he told ABC Television.

Dr Hewson, leader of the opposition from 1990 until 1994 when he was toppled by Alexander Downer, said Mr Abbott was an incredibly focused and determined opposition leader.

He said that was where Ms Credlin was very good because she kept him on track.

"He did go down in history as probably the most effective leader of the opposition in the sense that he made negativity an art form, but from the point of view of good government and reform processes and so on, it was a pretty disastrous period," he said.