Freedom of speech campaigners have attacked the UK Government for refusing to allow a popular Iranian children's illustrator to attend the Edinburgh International Book Festival.

Scottish PEN said the Home Office had an "unfortunate track record" of keeping writers and academics out of the country after Ehsan Abdollahi, whose books are published in English was refused a visa.

Officials, according to Mr Abdullahi's publisher, did not believe the writer had financial independence and that he would return to Iran after events in Edinburgh.

Mr Abdollahi, who is 37, claimed one reason for the refusal was that he was not married. "Since when being a single person has become a crime?" he asked.

Scottish PEN, whose members include some of Scotland's best known writers, said: "The worrying trend of countries using the visa process to undermine the freedom of writers to travel freely to communicate with others and share their work is a significant barrier to free expression and the sharing of literature across the globe. The restrictions put in place by the Home Office has an unfortunate track record of inhibiting artists and academics from visiting the UK.

"The PEN Charter reaffirms the belief that ‘literature knows no frontiers’ and Mr Abdollahi’s involvement at the book festival epitomised this belief. We are deeply saddened that such an opaque and bureaucratic process has restricted his ability to connect with the children who have derived so much enjoyment from his work. "

The Home Office does not comment on individual cases.