Just 79 per cent of patients referred for urgent suspicion of cancer were treated within 62 days in the last quarter of 2021, the lowest percentage since records began in 2006 and a drop of four percentage points on the previous quarter.
The Scottish Government target, which has never been hit, is for 95 per cent of eligible patients to be seen in this time.
Scottish Labour accused the Scottish Government of “dangerous negligence” for letting performance drop so far, while the Scottish Conservatives said lives are at risk.
Another target, for 95 per cent of patients to wait no more than 31 days for treatment after the decision is taken to treat them, was hit, at 97 per cent.
No health boards met the 62-day target, while NHS Grampian and NHS Highland failed to meet the 31-day standard.
Macmillan Cancer Support said the figures show that “a cancer care system that was struggling even before the pandemic began is now failing to cope with a rise in demand, despite how hard professionals are working.”
Janice Preston, Head of Partnerships for Macmillan Cancer Support in Scotland said: “Early diagnosis and timely treatment provides the best possible outcomes for people with cancer.
"These latest figures show that these two things are not in place and more people are now facing delays in receiving their life saving cancer treatments than ever before.
“We know that delayed and cancelled treatment can cause a huge amount of worry and distress and some people will have complex emotions associated with what might have happened had they been diagnosed or treated sooner.”
Labour health spokesperson Jackie Baillie warned of a “ticking timebomb” on cancer.
“Scottish Labour have long warned that there is a cancer timebomb threatening to wreak havoc with services and cost lives, and now this is starting to hit,” she said.
Scottish Conservative health spokesperson Sandesh Gulhane said: “These deeply concerning figures clearly show the pandemic has created a ticking timebomb when it comes to cancer diagnosis in Scotland.
“More and more patients are facing devastating delays which are harming their chances of survival. We know that the earlier a patient is diagnosed, the better their chance of surviving.”
The Scottish Liberal Democrats called on the government to “get a grip” on cancer care.
A Scottish Government spokesperson said: “The NHS remains under sustained pressure as a result of Covid-19, with the number of people awaiting diagnostic tests now at the highest level since 2018, and we are working tirelessly with health boards to provide vital services.
They added that £10 million of additional funding was directed to support cancer waiting time improvements in NHS Scotland across 2021/22, with a further £10 million for 2022/23.
"These funds are being directed across a number of specialties, with a strong focus on Colorectal and Urology – two of the most challenged 62 day pathways
"Initiatives include up-skilling nurses and investing in diagnostic tests to extended working days and weekend working, to increase capacity and both see and treat cancer patients as quickly as possible.”