SENIOR NHS officials and health board executives face being called before a Holyrood committee to respond to the damning revelations about waiting lists.

The Public Audit Committee will question Auditor General Caroline Gardner next week about her report on the subject, and this is likely to be followed by summons to NHS Scotland and health board officials as the committee delves into the controversy.

That may not be the end of the matter, as the Parliament's Health and Sport Committee is likely to pick up on evidence unearthed by Public Audit. At this point the row is likely to become highly political, as that committee decides whether to call Health Secretary Alex Neil, his predecessor Nicola Sturgeon or both to answer questions on the saga.

Findings this week have cast doubt on the accuracy of waiting times figures for thousands of patients in Scotland.

The problem surfaced in 2011 when NHS Lothian was found to have manipulated waiting time codes, marking patients as unavailable for "social reasons" such as failing to get time off work or being on holiday.

Facing extra pressure to meet shorter 18-week guarantees, it was discovered managers were putting pressure on staff to find ways around the system.

In its report, Audit Scotland found the use of "social unavailability" increased from 11% in 2008 to more than 30% in 2011.

The levels then dropped off around the time "fiddled" waiting figures were discovered at NHS Lothian.

Last night, the Scottish Government rejected the claim that the number of those affected by treatment delays, either because of medical reasons or because of social factors such as holidays, work commitments or personal preferences, had reached 42,000.

A Government spokeswoman said: "This is factually inaccurate. In June 2011, over 94% of all patients – including those who had periods of unavailability – were treated within 18 weeks. All of this information is published quarterly."

But the political row is not going to go away. Next week Ms Gardner will give evidence to Holyrood's Public Audit Committee, which is certain to probe the suggestion the problem was caused by a computer failure.

Labour remains deeply sceptical about this, arguing that if it was an IT problem it would be evenly spread across types of treatment. Instead, there are spikes in those suspended from lists in areas that are most under pressure, implying deliberate decision-making.

Public Audit Committee convener Iain Gray said: "The committee will question Caroline Gardner next Wednesday and will then decide what further inquiries they want to make. The usual procedures would be to ask the responsible accountable officer to provide evidence."

That implies NHS Scotland senior officials and possibly health board chiefs, rather than their political masters, but Health and Sport Committee convener Duncan McNeil made clear his committee would then consider looking at political accountability once Public Audit had completed its proceedings.

Holyrood committees all have a SNP majority, reflecting the balance in the chambers, so even committees chaired by Labour conveners could run up against fierce SNP resistance if it is perceived that they are looking to attack Mr Neil or in particular Ms Sturgeon.

Labour health spokeswoman Jackie Baillie made clear that the issue had some way to run. She said: "The argument that this is all down to the IT system is absolute rubbish. It is explicitly clear from the Audit Scotland report that the use of social unavailability was where there was greatest pressure and demand. Staff told the investigators that it was in those areas they used the code the most."

She added: "Instead of the bunker mentality when it comes to criticism, Alex Neil and Nicola Sturgeon should start taking responsibility."