Some independent special schools are exploiting their monopoly position to "take advantage" of local authorities, the leader of the Liberal Democrats has said.
The claim came during a parliamentary debate on SEND funding which saw MPs call for greater scrutiny of private special schools.
There are 540 non-maintained and independent special schools in England, which cater for children with complex needs, but Sir Vince Cable raised concerns that some schools could be “exploiting” their position.
“In many cases, the private special schools perform a very important function and are of very high quality, which is clearly why people seek them out,” he said.
“But there is certainly some evidence that those schools are exploiting monopoly provision and taking advantage of local authorities.
"In some cases, they should be referred to the Competition and Markets Authority. ”
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Fellow Lib Dem Sir Edward Davey MP added that more accountability was needed.
He said maintained state schools are "properly held to account for their budgets", but added that some voluntary or private schools are not.
He said: "This might be controversial, but in my experience, some of them do not provide the quality of care with the money they are given, partly because special needs are extremely difficult to look at.”
The debate in parliament’s Westminster Hall last week came after a local authority chief executive raised concerns about “aggressive marketing” by private special schools earlier the same day.
MPs on the Commons Education Select Committee heard John Henderson, chief executive of Staffordshire County Council, say he felt parents were being influenced by advertising.
He said: “There is quite some aggressive marketing out there - in terms of these provisions, in terms of ‘come to us’.”
But Claire Dorer, chief executive of the National Association of Independent Schools and Non-Maintained Special Schools (NASS) said that the comments were “unhelpful and somewhat disingenuous”.
“What we’re seeing is a systemic difficulty meeting the needs of children with SEND and it doesn’t help to blame one part of the system over the other,” she said.
She said that a survey of 300 parents by NASS in 2017 found that for 70 per cent of parents the current independent school place they had for their child was at least the third school their child had been to after other places had broken down.
For 11 per cent, it was at least their child’s fifth placement.
"Generally children enter independent and non-maintained provision after experiencing breakdown in other parts of the system," Ms Dorer said.
"So the idea that parents make the decision to place their children in residential provision on the basis of fancy marketing is not only unhelpful but insulting to parents about the difficulties they go through and the agonising they go through before they say that’s what they want for their child."
She added that it was not their experience that any school or group of schools were in a position equivalent to a monopoly in economic terms, and that independent schools have a legal requirement to report back to local authorities each year on how the fees were spent.
“While you have local authorities talking about a 'pull' of parents into our sector, our experience is that there is more of a push from local authorities to take children and young people because maintained special schools may well be excellent but most of them are full to bursting,” Ms Dorer said.
The DfE has been contacted for comment.