Health Secretary Jeane Freeman has apologised to almost 1,800 women who missed out on screening appointments for breast cancer.
Ms Freeman said it would be a “worrying time” for the the 1,761 women affected after a review of the Scottish Breast Screening programme discovered they had not received their final appointments.
As a result, some women will have the checks delayed for up to three years – with the charity Macmillan Cancer Support describing the situation as “incredibly concerning”.
Women in Scotland are invited to come forward for the screening, which is carried out in a bid to detect breast cancer before symptoms are noticed, between the ages of 50 and 70.
However, delays in the programme meant the women affected were not invited for their final appointment at the age of 70.
Janice Preston, head of services for Macmillan in Scotland, said: “It’s incredibly concerning that so many women in Scotland have not been able to have their final breast screening appointment.
“This will undoubtedly create a great deal of concern and anxiety for the women affected.”
The Scottish Government has already pledged tests will be carried out as quickly as possible and that this should not impact on the current breast screening programme.
Meanwhile, additional NHS staff are being put in place in a bid to provide reassurance to those affected.
Ms Freeman said: “I know this will be a worrying time for the women affected and I apologise fully for any distress caused.
“The women are being contacted as a priority and resources have been put in place to ensure they are screened promptly and offered any wider support needed.
“This additional screening will not delay other women attending their routine appointments.”
She continued: “This issue came to light following a due diligence review of the breast screening system in Scotland which was undertaken after a significant incident with England’s breast screening programme earlier this year.
Tory public health spokeswoman Annie Wells said women would be “extremely concerned that they have been overlooked”.
The Conservative said: “These tests are absolutely crucial in identifying and treating cancer at early stages. This obviously improves the chance of a good outcome for the patient.
“It is truly concerning to think that almost 2,000 women have missed this important screening and that they are still potentially undiagnosed.
“The Scottish Government must identify and communicate with those who have missed their screening urgently as well as reviewing procedures to ensure this never happens again.”
Liberal Democrat health spokesman Alex Cole-Hamilton described it as a “horrifying lapse of process”.
He continued: “It will be an anxious time for the women who are now discovering they have missed out on key screenings.
“The Scottish Government must remedy this at speed and ensure that no other women ever face the potentially devastating consequences of such a blunder again.”