The book 'And Tango Makes Three' tells the story of two male penguins raising a baby chick in Central Park zoo. Cover illustration: Simon & Schuster children's publishing

State-run libraries in Singapore have deemed a children's book about two male penguins raising a baby chick inappropriate and are to destroy all copies following complaints the content was against the city-state's family values.

The country's information minister Yaacob Ibrahim has said he supports the decision to pulp all copies of the book along with two other titles after the National Library Board (NLB), which runs 26 public libraries in Singapore, pulled them from the shelves.

The books are 'And Tango Makes Three', about a male-male penguin couple in the Central Park zoo; 'The White Swan Express: A Story About Adoption', which involves a lesbian couple; and 'Who's In My Family: All About Our Families'.

"The prevailing norms, which the overwhelming majority of Singaporeans accept, support teaching children about conventional families, but not about alternative, non-traditional families, which is what the books in question are about," Ibrahim said.

"Societies are never static, and will change over time. But NLB's approach is to reflect existing social norms, and not to challenge or seek to change them."

The decision triggered an online petition and an open letter to spare the books with thousands of signatures collected. Some are calling for a boycott of the libraries and their events.

Donald Low, author of 'Hard Choices: Challenging the Singapore Consensus', a book recommending policy reforms in the tightly-controlled south-east Asian state, said he had pulled out of the Singapore Writers' Festival in November to protest the decision.

"I see no evidence of a significant segment of Singapore society objecting to these books being in our public libraries, even if the majority of Singaporeans are conservative," Low said.

He objected to Yaacob's comments, saying that "attitudes are more complex and nuanced than the reductionist view the minister has taken.

"I've always believed that Singapore society is generally tolerant, open and relaxed about people whose sexual orientations are different from ours even if we don't agree with them," Low said.

In recent months, religious conservatives in the wealthy, multi-cultural city-state of 5.4 million people have become more vocal in opposing gay rights. On paper, gay sex remains a criminal offence in Singapore, although authorities rarely enforce the British colonial-era legislation.

Last month, Singapore witnessed its largest gay-rights rally with 26,000 in attendance.

It was not clear how and when the books will be destroyed.