The findings have sparked concern over the potential knock-on impact on treatment for patients with life-threatening conditions such as cancer.
The latest figures from Public Health Scotland show 98,332 Scots were still waiting for tests at the end of June, a rise of 7.6 per cent from pre-pandemic levels.
This included 68,407 who were waiting for radiology screening and 29,925 for endoscopy examinations.
The total number of patients on the waiting list was 11.4 per cent higher than the equivalent figure at the end of February - shortly before NHS Scotland put all non-urgent elective services on hold in mid-March.
Some 63,550 people – around 65 per cent of patients referred – waited for longer than six weeks.
Of the total, 41,463 (48.2 per cent) waited between 12 and 24 weeks, 25,721 (29.9 per cent) waited between 24 and 51 weeks, while 3,950 (4.6 per cent) had been waiting for a year or more.
The statistics show the number of patients being admitted began to increase on a weekly basis throughout the quarter, although admissions by the last week of June were still 70 per cent lower than in the last week of February.
Scottish health secretary Jeane Freeman acknowledged the difficulties Scotland’s health service has been contending with as a result of the coronavirus but insisted the most urgent cases would get priority.
She said: “The impact of the Covid-19 pandemic means there are significant operational challenges ahead for the NHS in Scotland, which are reflected in the statistics published today.
“In recent weeks, health boards have been carefully resuming a wide range of services, but the ongoing need for additional infection prevention and control measures means each clinic or theatre session will see fewer patients.
“However, those patients who require urgent, elective and vital cancer treatment have been, and will continue to be, prioritised.
“I recognise that there is a human story behind each and every one of these statistics, and that further delays can materially affect the quality of life of those waiting for care or treatment, with continuing pain and further anxiety.
“I am acutely aware of that, and want to be in a position where the NHS can speed up mobilisation as soon as possible – however the safety of patients and staff is always at the forefront of decisions taken.
“As we continue to deal with the virus we have to continue to balance demands and pressures, making the best decisions we can: none of which are easy and none of which are taken lightly.”
Cancer charities have expressed concern over the backlog and warned that action must be taken to ensure patients don’t “pay the price”.
Kate Seymour, head of policy and campaigns in Scotland for Macmillan, said: “While not all of those waiting for tests will have suspected cancer, many of them will.
“Waiting to find out whether you have a life-threatening illness is one of the most stressful experiences anyone will endure.
“Being finally diagnosed over three months after being referred for tests adds legitimate worries about how that wait may have impacted on their health and the potential consequences of a more advanced cancer requiring more invasive and debilitating treatment.
“While we know the pandemic has been extremely challenging for the NHS, people with cancer can’t be expected to pay the price.”
She urged the Scottish Government to get the cancer care system back on track as rapidly as possible, using “all available capacity to clear the diagnostics backlog.
Marion O’Neill, head of external affairs for Cancer Research UK in Scotland, said more healthcare workers and equipment and innovations to increase capacity were necessary to tackle the waiting lists.
She added: “Hospital services have had to rapidly adapt and innovate to manage the impact of the pandemic so far, and this will need to continue to prevent the number of suspected cancer cases mounting up further.
“The public also need to feel confident that, if they have suspected cancer symptoms, they will receive a test swiftly and safely, with minimal risk of exposure to Covid-19.
“Protecting diagnosis and treatment areas from the virus must be a priority. Increasing service capacity is also essential.”
Opposition politicians have condemned the waiting lists.
Scottish Liberal Democrat health spokesman Alex Cole-Hamilton said: “The number of patients waiting for key tests is alarming.
“Behind each case on this list is a person and a family wracked with worry.
“The legacy of this pandemic means the NHS is going to be playing catch-up on screenings and important appointments for months or years.
“This will be a mountain to climb and it’s incredibly important the Scottish Government ensures the resources necessary to clear the backlog are available.”
Monica Lennon, health and social care spokeswoman for Scottish Labour said: “With vital targets being missed by miles and thousands of patients queuing for treatment and tests, serious questions must be asked about the health secretary’s failure to steer our NHS through the pandemic.
“Jeane Freeman emptied our hospitals and cancelled thousands of appointments and it’s taken her five months to slowly get services up and running.
“With thousands of Scots waiting for key tests and languishing for months without treatment it is vital a plan to fully kick-start and support our NHS is implemented.
“Delays are putting patients at risk and that’s why ministers should be focused on their needs.”