SCOTLAND'S largest health board has been accused of massaging waiting time figures after it emerged one third of patients were marked as unavailable to attend appointments.

Dr Richard Simpson will call for an investigation into figures produced by NHS Greater Glasgow and Clyde which are more than 10 per cent higher than any other mainland health board.

Patients who are marked as unavailable for treatment are suspended from waiting time guarantees.

Latest figures show 33 per cent of patients queuing for treatment in the NHS GGC area were marked unavailable at the end of December

NHS GGC claim the high number of patients marked unavailable for hospital dates could be attributed to seasonal factors

But official graphs suggest at least 30 per cent of patients were unavailable in the region at most of the quarterly checks carried out last year, while for Scotland as a whole the figures sit little over 20 per cent.

Nearby health boards such as NHS Lanarkshire have lower that average levels while rates are down to 12 per cent and below in NHS Fife.

Under the Scottish Government's system of waiting times targets patients queuing can be frozen if they cannot accept appointments for a range of reasons - such as holidays, work commitments and illness.

This means the clock calculating how long they have spent queuing for treatment is stopped until they become available again.

Concern about patients being suspended from waiting time guarantees was sparked by a scandal in NHS Lothian when it emerged patients were being offered appointments at short notice in England and then being marked unavailable for treatment when they could not accept them.

Dr Richard Simpson, Scottish Labour public services spokesman and a former GP, said: "The last time we had significant variations in waiting times was the Lothian situation which led to the Lothian scandal and we discovered that there was manipulation in the Lothians and that Audit Scotland could not prove that there was not similar manipulation in other health board areas.

"If one in three patients are socially unavailable I suspect either there could be manipulation or the appointment system is being run in such a way it makes it impossible for patients to come."

He is planning to table questions in Holyrood asking about the situation.

The latest figures for unavailability in NHS GGC were published alongside data showing thousands of patients are still waiting more than 12 weeks for treatment doctors have said they need even though the Scottish Government enshrined this waiting time guarantee in law.

At the end of last year, 2185 people queuing on waiting lists across Scotland had been waiting for more than 12 weeks - a figure that has risen steadily since the law came in.

The same report showed on December 31 in NHS GGC 33.1 per cent of patients were unavailable for treatment, 27.8 per cent in NHS Shetland and 21.3 per cent in NHS Grampian.

In Glasgow this means 5437 patients were recorded as unavailable, the highest figure logged for the board and up from 3115 in December 2012.

In a statement NHS GGC said: "It is not uncommon for patients to choose to delay a planned procedure.

"This has a seasonal factor, which means this is more likely to happen around the festive period.

"These figures reflect patient choice at a busy time of the year."

A Scottish Government spokesman said: “We have very clear guidance for TTG (the treatment time guarantee) that all boards are required to follow. We are in discussion with NHS Greater Glasgow and Clyde regarding their higher than average levels of unavailability.”