"So you are married to a monkey and have two little yardapes. Good job. Got bananas?" This is one of the letters and emails that my Ghanaian wife and I received, when we asked that the Hergé book Tintin in the Congo be removed from the children's sections of bookshops back in 2007.

One Saturday in June of that year, I was in the children's section of Borders in St Albans with my wife and our two little boys, then aged two and seven. They sat on soft chairs while I selected a book for them to read. My attention was immediately drawn to a two-metre tall, bright red display in the shape of a rocket. The display was to highlight Tintin books, and the first that caught my eye was Tintin in the Congo. As with many people of my age, I had fond memories of the adventures of the boy detective and his dog, Snowy.

Before passing the book to my wife and two boys, I flicked it open. I was astonished to see page after page of graphic representations of black African people as sub-human monkey people, bowing before a white teenager, worshipping his dog as a god and incapable of proper speech. In fact, the only black monkey caricature in the book who could speak English properly was a chimpanzee.

I showed the book to my wife, Gifty, whose face fell as she leafed through it. We immediately took the matter up with the manager of the superstore, and later with their regional manager. We asked why such extraordinarily racist material was being targeted at children. We were told that the book was a collector's item. We asked if their chain sold collector's editions of hardcore pornography or Nazi anti-Jewish propaganda cartoons in the children's sections. They did not.

My wife and I were horrified that our children, and other children across the UK, were being exposed to depictions of themselves, their parents and their friends as sub-human ape people. We mounted a campaign – not to have the book banned, but merely to have it removed from the children's sections of bookshops.

There was fierce resistance initially, and routine comments from otherwise serious writers and radio presenters of "political correctness gone mad" – almost always by people who had not seen the book. Despite this, we eventually received assurances from Borders that the book would be removed from children's sections of bookstores across the UK, US, South Africa and Australia, and placed in the adult graphic section. Waterstone's subsequently also adopted the policy.

This week, however, I was informed the book had been found in the children's section of a Waterstone's store, although with a warning label on its cover. The book is also currently available from the children's section of the Waterstone's website; its synopsis notes that the book "reflects the colonial attitudes of that period in its depiction of African people".

I am a human rights lawyer, have won an award for my work on behalf of Gurkha veteran soldiers, and continue to campaign fiercely for freedom of expression, and against racism and victimisation. I would oppose the banning of any book. I also think Steven Spielberg's new Tintin film is fantastic. Spielberg, of course, is renowned as someone who has done a huge amount to preserve the testimony of Holocaust survivors.

Books are precious, but so are the minds of young children. It is vital that our children learn and explore the grotesque history of slavery, racism and antisemitism, but in the proper context of the school curriculum. The days of childish taunts in the playground of "monkey", and worse, are long gone, and booksellers must be careful not to undermine that progress.