An academic was yesterday dismissed as belonging "to the flat-earth society" after he again questioned the existence of dyslexia.

Professor Julian Elliott, an educational psychologist at Durham University, had previously claimed the condition was an "emotional construct". Yesterday, he labelled dyslexia an excuse for middle-class parents who did not want their children to be considered low achievers.

He said dyslexia had become a term used by parents worried their children's reading problems would brand them "lazy, thick or stupid" and said it should be rediagnosed as a reading difficulty.

His comments came on the back of complaints by lecturers that more students are being given extra time to complete coursework and exams.

But his statements angered campaigners and experts.

Dr Adam Hannah, an Ayr-based GP, is one of the leading figures within Dyslexia Scotland. He said: "It is true that dyslexia is a very complex condition and complex conditions always have their critics.

"But it is the largest group of any learning difficulty, with an estimated one person in 10 having dyslexia compared with one in 1000 with autism.

"It has also been a known condition for over 100 years. We've heard this before from members of the flat-earth society, who produce wild statements with no scientific basis. The main problem is that teachers are not being trained to identify it."

Catriona Collins, who works with a cross-party group at the Scottish Parliament examining dyslexia and has championed the need for children with the condition to receive individual teaching, gave Professor Elliott's latest comments short shrift.

She said: "The only thing I can say about this is that dyslexia definitely does exist."

Two years ago Professor Elliott said poor readers wanted to be called dyslexic because of a "wrong" perception that dyslexics were clever.

He added that, after 30 years in the field, he had "little confidence" in his ability to diagnose it.

Yesterday he reiterated that he had no evidence to identify the condition.

He said: "After years of working with parents I have seen how they don't want their child to be considered lazy, thick or stupid.

"If they get called this medically diagnosed term, dyslexic, then it is a signal to all that it's not to do with intelligence."

The professor said the symptoms of dyslexia, such as clumsiness and letter reversal, were similar to those seen in people who simply could not read.

Professor Elliott teaches at the School of Education at Durham University.

He taught in mainstream and special education before becoming an educational psychologist.

In 2005 he contributed to the controversial Channel 4 documentary, The Dyslexia Myth, which cast doubts on the condition.

John Rack, head of research and development with the charity Dyslexia Action, said: "There is ample evidence that dyslexia exists across the spectrum and the argument that there is no consistent means of identifying it is one cited by people who don't know enough about the subject."

Tomorrow, a Scottish Executive-organised conference on the condition will be held in Edinburgh. The event will feature Sir Jackie Stewart, president of Dyslexia Scotland, and a leading expert on the issue, Professor Martyn Rouse of Aberdeen University.