NHS Grampian has been the worst performing health board in Scotland against a key waiting-time target for 15 consecutive months.
The north-east’s board achieved the 18-week referral-to-treatment standard for just 66.9% of its patients in June, down from 68.7% in May.
Its performance means one out of every three patients in the region waited longer than they were supposed to for treatment.
The health board’s failures have seen it outperformed by every one of Scotland’s other health boards since March last year.
In contrast, the latest figures show that NHS Highland met the target for 82.6% of patients in June, while 85.5% of NHS Shetland patients were treated within 18 weeks of referral.
NHS Orkney was at 92.3%, while NHS Western Isles recorded 94.8%.
Since December 2011, the Scottish Government’s standard has been for 90% of patients to wait no longer than 18 weeks from referral to treatment.
NHS Grampian has not reached the target, nor been above the Scottish average, in any month since September 2014.
Last night, an NHS Grampian spokeswoman said: “We are committed to meeting the waiting times targets laid down by the Scottish Government and acknowledge our current performance falls short of that.
“This is due to longstanding issues in recruiting for some specialist medical and nursing vacancies.
“Where we do not achieve the waiting standards set we actively manage the lists and ensure that patients are treated as soon as possible and in line with their clinical priority.”
Across Scotland, a total of 82.8% of patients were reported as being seen within 18 weeks in June, up from 80.9% in April and 82.6% in May.
Health Secretary Jeane Freeman highlighted a survey of hospital inpatients which showed 86% described their care as positive, while 91% positively rated the staff who had looked after them.
She said: “NHS investment and staffing are at historically high levels and the record high inpatient satisfaction rates published today are a testament to the hard work of our frontline NHS staff.
“However, meeting the challenge of improving performance and reducing waits requires the twin approach of investment and reform.
“That is why we recently allocated an additional £6 million to reduce waiting times for endoscopies, with a focus on the most urgent patients, including those with suspected cancer.
“That is seeing immediate steps to cut the number of people across Scotland waiting for diagnostic testing, with health boards working towards reducing the number of patients waiting over six weeks by 5,000 by the end December 2018.”