The government has rejected the claim made in a television documentary that dyslexia does not exist.
Education minister Lord Adonis said dyslexia was a "complex neurological condition" and that denying it had caused parents understandable anxiety.
He told peers dyslexia was a "complex neurological condition" and that people with it needed proper support.
A row erupted after a Channel 4 programme, The Dyslexia Myth, cast doubt on the condition.
Reassurance for parents
During a House of Lords debate, Lord Adonis said: "The very title of that programme gave rise to understandable anxiety that children's needs might no longer be recognised and supported.
"It is important that we reassure parents that this is not the case.
"Let me state, clearly and categorically, the government's view that dyslexia is a complex neurological condition and that people with dyslexia do need proper support to develop the reading, writing and comprehension skills essential to succeeding in school, in life and in work."
Some parents say they have trouble getting schools or education authorities to recognise their children's difficulties, however.
Lord Adonis was responding to a question from Liberal Democrat peer Lord Addington, vice president of the British Dyslexia Association.
He asked the government to reaffirm dyslexia's status as a disability.
"Will the government confirm that they acknowledge the existence of dyslexia? Do they accept that it is a neurologically-based condition?
"The definition I have states that dyslexia is an ectopic condition, which means that cells migrate to the wrong place in the brain. It is a real medical condition."
A Durham University professor also questioned the scientific validity of the term "dyslexia".
Julian Elliott said it was largely an "emotional construct" and there was no consensus on how to diagnose or treat it.