Not all patients have the same status for treatment under executive rules

Some patients do not have a guarantee about when they will be treated if they cannot attend an appointment for personal, social or medical reasons.

The SNP's Nicola Sturgeon has called for an investigation into the matter.

But the executive said it was planning to change the system by 2007 to make it clearer and "fairer to patients".

SNP deputy leader Ms Sturgeon accused Health Minister Andy Kerr of misleading the Scottish public over waiting times in the NHS by using "hidden waiting lists".

There are currently 112,000 people waiting for an operation in Scotland.

These waiting lists should not be used to hide the true scale of the number of people waiting for treatment in Scotland Nicola Sturgeon SNP

However, more than 34,000 of them are given an Availability Status Code which means they do not qualify for the executive's guarantee of treatment within nine months.

A spokesman for the executive said: "There is no secrecy about Availability Status Codes (ASCs) and how they are applied.

"And we have already announced that we are abolishing them by 2007 to make the whole system clearer, more consistent and fairer to patients.

"Use of ASCs is governed by national guidance to ensure that patients are not disadvantaged. We expect boards to follow them and have received repeated undertakings from boards that this is the case."

But Ms Sturgeon has maintained that an independent investigation should be carried out to ensure a full and true analysis of the situation.

Spinal injury

She said: "These waiting lists should not be used to hide the true scale of the number of people waiting for treatment in Scotland.

"This is yet another example of the health minister bending figures to mislead the public and hide the abysmal reality of waiting times in Scotland.

"There must be an immediate investigation by the Auditor General to ensure there is independent analysis to reveal the true extent of waiting lists and waiting times in Scotland."

Walter Knight has been waiting for his operation for 18 months

Walter Knight from Dumfriesshire has been waiting 18 months for an operation to ease a spinal injury which is so severe he finds it difficult to sit or lie down.

His wife Jan said: "Walter finds it difficult to sleep at night, he just cannot get comfortable. We bought our car because the seating was so good in it and he sleeps in that.

He was scheduled to have an operation at the Western Infirmary in Glasgow.

But after months of scans and appointments, Mr Knight is still waiting for his treatment.

He said: "I was told I had to lose some weight, I lost the weight and phoned to say that I had lost the weight. I was then told to lose another stone in weight, they just keep moving the goal posts."

The executive spokesman said he was concerned to hear of Mr Knight's case and the inconvenience he had suffered.