Jens David Breivik, a former diplomat who lives in retirement in the south of France, told the Swedish newspaper Expressen: "I couldn't believe my eyes."
"I don't feel like his father," he said. "How could he just stand there and kill so many innocent people and just seem to think that what he did was OK? He should have taken his own life too. … I will have to live with this shame for the rest of my life."
The interview was reported by CBS.
Breivik's parents divorced in 1980, soon after his birth, and his father lived in London. The elder Breivik said he and his son have had little contact since 1995 when Anders was 16.
Asked what he would say to his son, Breivik said, "He must live in another world. I do not think he would understand."
French police surrounded the father's house Monday to protect him from throngs of reporters.
Anders Behring Breivik has admitted bombing downtown Oslo and slaughtering scores of young people at a camp Friday.