Dyslexia charities have rejected claims that the condition is a label used by middle-class parents who do not want their children seen as low achievers.
The suggestion that dyslexia does not really exist has angered parents
The British Dyslexia Association and Dyslexia Action said people with dyslexia had a "very real" problem.
They were responding to claims from Professor Joe Elliott, an educational psychologist at Durham University's School of Education.
Professor Elliott said the term dyslexia was becoming meaningless.
But the British Dyslexia Association and Dyslexia Action said that, to the six million people in the UK living with dyslexia, it was very real.
"Dyslexia is a complex condition which affects each person differently and it is irrespective of intelligence, race or social background," the organisations said in a joint statement.
"The severity and different difficulties any one dyslexic person may present can vary. It is for this reason that definitions of dyslexia are not always consistent.
"Once again dyslexia seems to be making the headlines for all the wrong reasons. It is frustrating that the focus should be on whether dyslexia exists or not and claims that it does not is very upsetting to the one in 10 people that it effects.
"The question should be what can be done to help people with dyslexia and those with literacy difficulties?"
The charities said the effects of dyslexia could be minimised by targeted literacy intervention and technological support.
They said the education system should look to identify and support all children at risk of reading failure.
There have been previous claims that dyslexia was being too widely applied or was not an authentic learning problem.
A television programme carrying such claims prompted Schools Minister Lord Adonis to defend the condition to the House of Lords.
He told peers that dyslexia was a "complex neurological condition" and that people with it needed proper support.
Dyslexia is defined by BBC health expert Dr Rob Hicks as "a congenital and developmental condition that causes neurological anomalies in the brain.
"It includes a range of types of learning difficulties where a person of normal intelligence has persistent and significant problems with reading, writing, spelling and sometimes mathematics and musical notation."