There may be some truth to the claim that some children are being diagnosed as such by schools which have simply failed to teach them or by parents who can't accept that their child is thick. That doesn't mean that that the condition doesn't exist though, the fact that some people do well on all verbal tests of intelligence and have siblings and peers that can all read perfectly well but be functionally illiterate themselves suggests that there is a condition that impairs reading.
This shouldn't be too surprising seeing as writing is something which was only invented a few thousand years ago and became widespread less that 200 years ago. In other words this kind of close scanning of symbols is not a skill we evolved with.
He claims that:
If dyslexia really existed then countries as diverse as Nicaragua and South Korea would not have been able to achieve literacy rates of nearly 100%.
There can be no rational reason why this ‘brain disorder’ is of epidemic proportions in Britain but does not appear in South Korea or Nicaragua
I don't believe the figure for Nicaragua and won't unless someone provides evidence besides which there wouldn't be anything particularly unusual about a disorder being more prevalent in one population than another.
(it is also pretty damning that according to Professor Julian Elliot there are 28 different definitions of dyslexia).
Is it? There are many definitions of species but we can all agree that there is a fundamental difference between a buffalo and a lettuce. There are many concepts that have different definitions- poverty, sex, intelligence, racism and species all spring to mind- that still reflect reality.
He also confuses illiteracy with dyslexia, many dyslexics can read even if they have more difficulty than others of similar intelligence in doing so. Undoubtedly there are some teaching methods that are more effective than others but that hardly invalidates the concept.
His postbag won't be bulging with angry letters but he is wrong none the less.