An esteemed children's author has accused John Lewis of plagiarising one of his stories for their latest Christmas advert.

Moz the Monster was unveiled on 10 November and tells the story of a little boy called Joe who finds himself tossing and turning each night unable to fall asleep. Until one night he discovers Moz, a cuddly seven fott imaginary monster, hiding under his bed.

Chris Riddell, a former children's laureate, posted a video featuring the two-minute festive commercial alongside pages from his 1989 picture book Mr Underbed, which also features a large blue monster who lives under children's beds.

"John Lewis help themselves to my picture book," the author wrote alongside the post which has been retweeted almost 2000 times.

Speaking to the Guardian, he stated that while the idea of a monster under the bed is not a new concept, he was stunned by the similarity of Moz The Monster, which was created by John Lewis' long-term agency Adam&Eve.

"It was the first picturebook I wrote and illustrated and was published in 1986. Subsequently, at the publisher's request, I re-illustrated it in 2009. During my time as children's laureate I spoke about Mr Underbed often at public events, as my first book."

A John Lewis spokeswoman said: "The story of a big hairy monster under the bed which keeps a child from sleeping is a universal tale which has been told many times over many years.

"Ours is a Christmas story of friendship and fun between Joe and Moz The Monster, in which Joe receives a night light which helps him get a good night's sleep. The main thrust of our story is utterly different to Chris Riddell's."

Despite denying the plagiarism allegations, the retailer was criticised online, with some encouraging the purchase of Riddell's book to give him the credit he deserves.

One person wrote: "Here's an idea. Why not buy Mr Underbed by @chrisriddell50 to let @johnlewisretail exactly how we feel about their #Christmas ad? #MozTheMonster."