Singapore's state-run libraries have deemed three gay-themed children's books inappropriate.

Citing complaints against the books, the National Library Board, which runs 26 libraries in Singapore, pulled the books from the shelves and said it would destroy the titles.

Similar themes about gay families run through the books, which are And Tango Makes Three, The White Swan Express and Who's In My Family: All About Our Families.

And Tango Makes Three was inspired by the real-life story of a penguin family with two fathers living in New York's zoo.

On Friday, the government backed the decision to scrap the books.

“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,” Minister of Communications and Information Yaacob Ibrahim is quoted as saying by the AP.

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

Thousands of people have joined an online petition asking the library to reverse course.

Gay sex is a criminal offense in Singapore, though the law, a holdover from British colonial rule, is rarely enforced.