The book – 'Micsoda csalad!' ('What A Family!') – is a Hungarian translation of two titles by US author Lawrence Schimel and Latvian illustrator Elina Braslina: 'Early One Morning', and 'Bedtime, Not Playtime!'. It features stories about the everyday life of young children of same-sex couples.

Pest county commissioner Richard Tarnai told Hir TV that bookstore chain Lira Konyv has been fined 250,000 forints ($825) for violating the country's advertising law by not displaying a warning about the content of the book. "They should have specifically indicated that the book's content deviated from the norm," Tarnai said.

Tarnai argued that the book was placed next to classic children's stories, which could mislead customers.

The Lira Konyv book chain said it found the fine "surprising" and is preparing a legal response. It added that a sign will be put in place warning customers that the store sells "books with different content than traditional ones."

The book's Hungarian distributor, the Foundation for Rainbow Families, released a statement saying that the book depicts "completely normal, ordinary families," and that the sexuality of parents is not the focus of the story.

"These families haven't had their own story book so far. That's why we thought it was important to publish a fairytale book about them – and first of all for them," the distributor said.

Schimel accused the Hungarian government of "trying to normalize hate & prejudice with these concerted attacks against books like mine." He told The Guardian newspaper that he wanted to celebrate queer families, but claimed that the fact that children in his books have same-sex parents is "incidental to the story."

Hungary, which is ruled by a conservative government, passed a law last month banning LGBT content from the school curriculum and children's TV shows.

The legislation was sharply criticized by EU officials. European Commission chief Ursula von der Leyen said that the law discriminates against LGBT people and goes against the key values of the EU. She threatened Budapest with repercussions unless the law is changed.

Hungary has rebuffed the attacks from the EU. "Brussels can't tell people how they should raise their children," the Hungarian prime minister's Chief of Staff Gergely Gulyas said on Wednesday, adding that the law is aimed at protecting minors.