Some leading stores plan to boycott a book by the Kahui twins' mother, Macsyna King, after a public outcry - a move the writer has slammed as the "death of free speech".

The Paper Plus group and The Warehouse yesterday said they would not stock Breaking Silence: The Kahui Case because of an overwhelming outcry from the public.

Last night, 30,000 people had joined the Boycott the Macsyna King Book Facebook page.

Whitcoulls is expected today to make an announcement on whether it will join the boycott.

Author Ian Wishart defended the book, saying the stores had given in to unfair public pressure.

"I am saddened that New Zealand booksellers, who have been going through a hard time in recent months, have fallen victim to a Facebook lynch mob campaign.

"It's a sad day for the New Zealand media because if we can't tell stories by going to both sides and getting people to speak up because it offends various groups in the community, then freedom of speech is being seriously threatened.

"And also the rights of New Zealanders to buy books."

The Warehouse's general manager of merchandise, Nick Tuck, said: "We have received significant comment from our customers today both directly and online with regards to this book.

"Overwhelmingly, they have told us that they do not wish to buy it or see it on the shelves."

Paper Plus chief executive Rob Smith said: "The prevailing opinion is that our stores do not feel comfortable selling this book and our customers do not want to buy it."

A large number of people had posted a generic comment on various retailers' Facebook pages - including Booksellers NZ - saying they would boycott any shop that had anything to do with the book.

Booksellers NZ yesterday released a statement clarifying that it was a membership organisation set up to support book retailers.

"We have never and will never ask or tell any of our members not to stock a particular title. The titles they stock are their choice as individual business owners."

Wishart, editor of Investigate magazine, said he had not expected the book to get the kind of reaction it has, with people calling for murder on the Facebook group page.

Wishart told NZPA yesterday that Ms King would not get a cent of royalties from the book, which is due out at the end of next month.

He wrote the book after Ms King contacted him last year. She did not trust journalists but wanted to tell her story, he said.

Asked whether Ms King regretted her decision to speak out through the book, Wishart said no, but she was becoming afraid of how people would react towards her.

"She's holding up. She's obviously very sad about the reaction from people and she's fearful of what the lynch mob might do."