The only known portrait of Jane Austen is to be sold by auction in New York this week, and is expected to fetch between ￡200,000 and ￡400,000.

The oil painting, which experts believe was commissioned by the novelist’s great-uncle in 1790, has been handed down from generation to generation and currently belongs to one of Jane Austen’s descendants.

There has been some doubt over the authenticity of the portrait because some experts say the type of dress she is wearing in the painting is from the wrong historical period.

However, other academics and the auction house Christie’s, who are selling the painting, say the picture is a "true depiction" of the writer.

This is not the first time Jane Austen’s image has caused controversy. Earlier this year her publishers were criticised for giving her a makeover on the cover of a book about her life.

The publishers made changes to a sketch of Jane drawn by her sister. In the original picture Jane is wearing a cap, but in the new image the publishers have removed the cap, and added make-up and hair extensions.

Whatever she looked like, Jane Austen remains a British national treasure. Her books, such as Emma, Sense and Sensibility, and Pride and Prejudice, remain widely-read and have been successfully adapted for television and cinema.

In fact, her work is still so popular that in a recent survey to mark World Book Day, the British public voted Pride and Prejudice the nation’s favourite read – ahead of Harry Potter and The Lord of the Rings!