Security concerns have forced controversial author and anti-Islamic activist Ayaan Hirsi Ali to pull out of a planned speaking tour of Australia.

Hirsi Ali, who lives with round-the-clock security protection due to her criticisms of radical Islamists, was due to speak at events in Brisbane, Melbourne, Sydney and Auckland this week.

She was also due to appear on ABC's Q&A panel on Monday night. Her spot on the ABC talkshow has now been filled by federal energy and environment minister Josh Frydenberg and the Opposition's human services minister Linda Burney.

Organisers of her trip Think Inc said they were disappointed at her last-minute cancellation.