The executive director of the Anne Frank Trust has slammed a new teen novel which suggests Anne and a teenager hidden with her in wartime Amsterdam, Peter van Pels, had a sexual relationship.

Gillian Walnes said that the book "Annexed", which is a fictionalised diary by Peter, was “cashing in” on the diarist.

The book, published by Andersen Press, is a new novel from British author Sharon Dogar, who has written two other "coming-of-age" books for teenagers.

Ms Walnes said: “We are 99 per cent sure Anne and Peter never had sex. In fact we have a very poignant letter that Anne wrote to her father after he expressed his concern about how much time the two spent together alone. And she writes to him how upset she is by his lack of trust in her.”

Anne, who died aged 15 in Bergen-Belsen concentration camp, shared her first kiss with Peter, who was one year older. On March 3, 1944, she wrote: “The boy has such warmth in his eyes; I believe I’m pretty near to being in love with him.”

Anne Frank’s cousin and only living relative Buddy Elias told the Sunday Times: “Anne was not the child she is in this book” and said that the “terrible destiny” the two suffered was not material for fiction.

But Andersen Press urged people to read the book before making judgement, and said that it was not gratuitously sexual.

Publisher Klaus Flugge told "The Bookseller": “There are no sexual scenes in it. I think it's a wonderful book and it's not salacious or controversial at all.”