Publisher cancels alt-right blogger's book

Right-wing provocateur Milo Yiannopoulos' publisher has cancelled his planned book after a video emerged of the him defending sex with children.

Simon & Schuster and its Threshold Editions imprint announced on Monday that "after careful consideration" it had pulled the book, Dangerous, which had been high on Amazon.com's best-seller lists and was the subject of intense controversy.

The book deal was for a reported $US250,000 ($A325,000) and prompted outrage from the outset, including calls to boycott Simon & Schuster publications and threats from authors to take their work elsewhere.

"They cancelled my book," Yiannopoulos confirmed on his Facebook page.

"I've gone through worse. This will not defeat me."

The cancellation came just hours after the American Conservative Union (ACU) withdrew its invitation for the Breitbart News blogger to attend the Conservative Political Action Conference, which begins on Wednesday.

"Due to the revelation of an offensive video in the past 24 hours condoning pedophilia, the American Conservative Union has decided to rescind the invitation," ACU chairman Matt Schlapp said in a statement.

Yiannopoulos had been set to deliver the keynote speech at the conference, which is to be attended by top Republicans including White House political strategist Steve Bannon, who used to run Bretibart.

In the video, Yiannopolous says the idea of consent is "arbitrary and oppressive", and goes on to compare sexual relationships between older men and children as young as 13 to gay relationships between older and younger men.

He also speaks approvingly of his own sexual relationship with a 29-year-old priest when he was 17.

In response to being uninvited from the conference, Yiannapolous, wrote on Facebook he was "horrified by pedophilia", but his "usual blend of British sarcasm, provocation and gallows humour might have come across as flippancy, a lack of care for other victims or, worse, 'advocacy'."

Yiannopoulos writes for Breitbart News, considered by many a platform for the so-called "alt-right" movement, an offshoot of conservatism that mixes racism, white nationalism and populism.