By Gary Eason
Education editor, BBC News website
A council has been told that the way it is treating children with more serious special educational needs is illegal.
Part of the letter telling Surrey to make changes
Surrey County Council says it will comply with a Department for Education and Skills order to amend the special needs "statements" it has issued.
Parents had complained that the extra help their children should receive was not specified, as it should be.
Campaigners say similar malpractice is going on elsewhere. The councils argue they are devolving funding to schools.
Parents are said to have made complaints about Hertfordshire, the London boroughs of Ealing and Southwark, Reading, Windsor and Maidenhead, Kent and Bedfordshire, among others.
Surrey, according to the letter sent to the council by the department (DfES), had adopted "a blanket policy of never quantifying special educational provision in children's statements".
The whole point of a statement, which is issued after an assessment of more difficult SEN cases, is to set out a child's needs and the special educational provision that will meet those needs.
The courts have ruled this must be "specific, detailed and quantified".
The department's letter said it did not appear that Surrey was failing in its duty to assess children.
But it was not clear from the statements it was then issuing "how the school and the child's parents are to know what the authority has determined should be provided for the child".
The letter, from Phil Snell of the department's SEN division, said the education secretary was satisfied Surrey was failing to discharge its duty as set out in the 1996 Education Act.
It was dated 4 January and gave the council five working days to confirm it would comply with the law and 15 working days to send amendment notices to parents - explaining to them why it was making changes and what their rights were.
Mr Snell asked Surrey to confirm how many statements would need amending in this way.
The department said on Friday it had received "a positive and helpful response" from Surrey County Council to the concerns raised in its letter.
It added: "That correspondence is continuing."
A spokesperson for the council said it was in the process of amending its statements, as instructed - but they had been sent to the DfES for approval and had not been questioned until now.
The change would have no effect on the level of provision it was making: children were getting what they needed.
"The strategy for intervening at the earliest stage in supporting children with special educational needs has been considered by the DfES, which found it to be appropriate."
Marion Strudwick of the charity SOS!SEN, which helps parents in such cases, said Mr Snell's letter was useful ammunition.
If Surrey did not comply with the law it could now be challenged in the High Court.
"Phil Snell's letter is quite powerful," she said.
"It's an important move to stop this trend of saying, 'OK we will just give the money to the schools and let them decide what to do with it'," she said.
She said Surrey was one of the worst offenders but other authorities had also adopted similar policies.
Instead of detailed statements, they used vague phrases such as saying a child would "have some specialist teaching", without saying how much or who would provide it.
The school might be told it would receive funding for this - but without the amount being specified or ring-fenced.
"It's a practice that local authorities are trying to get away with far too much," she said.