Parents have clashed over claims the children's beloved lift-the-flap book Dear Zoo is 'biased' because all the animals are male.

Rod Campbell's 1982 book tells the story of a young boy who writes to a zoo to ask them to send him a pet.

He then receives a series of animals including a snake, a monkey and a 'too tall' giraffe before being given a 'perfect' puppy.

Rod Campbell's 1982 book tells the story of a young boy who writes to a zoo to ask them to send him a pet

Campaign group Let Toys Be Toys discusses the book in a blog post. The group, which calls for the toy and publishing industries to `stop limiting children’s interests by promoting some toys and books as only suitable for girls, and others only for boys,' describes the `skew' in children's books.

Blog poster Jess Day says: `Speaking personally, what’s even odder is that I’d read it to my small daughter about 200 times before I noticed.'

`We’ve all been surrounded by this bias all our lives, and it’s hard sometimes even to see it.'

The blog says: `No female animals in this zoo.'

Some parents commented that they agreed, the Sun reported.

One, Eliza Howard, said the book needs a 'modern-day re-write' or to be taken off shelves entirely.

Campaign group Let Toys Be Toys have now claimed the story is 'biased' - because all the animals involved are male

But some, including father-of-two Reuben Williams, don't see a problem with the picture book - which has sold some eight million copies worldwide.

He said: 'It's a classic and a best-seller for a reason.

'There's no issue unless you make one.'

The Dear Zoo and Friends website describes the story, designed for three to five year olds, as 'a must have for every child's bookshelf'.

It says: 'Young children will love lifting the flaps to discover the animals the zoo has sent - a monkey, a lion and even an elephant!

'But will they ever manage to send the perfect pet?'

The popular story has inspired a series of spin-off tales and gifts, including pocket editions and a Dear Zoo live show.