The Royal College of Emergency Medicine labelled the figures "deeply concerning and distressing”, warning the NHS is in a “serious crisis”.
Just 67.4 per cent of patients visiting A&E were seen and admitted, transferred and discharged in the week to January 9, according to new figures from Public Health Scotland.
This is the lowest percentage since records began in February 2015, and below the previous record of 69.6 per cent, set at the end of October last year.
It is also a drop on the previous week, at 71.6 per cent, which covered the Hogmanay period. The Scottish Government target is 95 per cent.
The percentage of people waiting more than eight hours and over 12 hours are also both at their lowest on record, at 90.2 and 96.7 respectively.
This is the first week that over 2,000 patients have waited more than eight hours, at 2,079.
Some 690 people waited more than 12 hours.
Dr John Thomson, Vice President of the Royal College Emergency Medicine in Scotland, said the figures were “shocking”.
"Staff are working exceptionally hard but are burnt out and overwhelmed and face moral injury on every shift,” he said.
"Patient safety is frequently compromised. We know long waiting times increase the risk of death and patient harm.
"The exit block that exists in our Emergency Departments which prevents patients moving in a safe, timely manner to an appropriate ward is worsening, causing even more harm to our patients.”
Numbers of people visiting A&E each week have dropped amid campaigns from health boards urging patients to seek advice from their GP or NHS 111, but remain at higher levels than during earlier waves of the pandemic.
Some 21,163 patients visited A&E in the week to January 9, while 6,902 of them waited more than four hours.
It comes as health boards across the country have warned of exceptional pressure due to high demand, staff absences and unfilled vacancies.
Health secretary Humza Yousaf has said the coming weeks will be among the most difficult the NHS in Scotland has ever had to face.
Scottish Labour’s health spokesperson Jackie Baillie labelled the figures “unacceptable”.
“This is a deeply worrying development and it is clear that thousands of lives are being put in danger,” she said.
Ms Baillie added: “NHS staff are working incredibly hard, especially as the winter pressures start to bite, but they are being badly failed by a Government that is not adequately supporting them in their efforts to keep the people of Scotland safe.”
Liberal Democrat leader Alex Cole-Hamilton said: “This is shocking. People are waiting too long to get care and treatment. NHS staff are under unimaginable pressure and working in impossible conditions.
"It harms the mental and physical wellbeing of staff as well as patients. This is not sustainable.”
Scottish Conservative health spokesperson Dr Sandesh Gulhane called the figures “shameful”.
“The tragic reality is that these delays lead to needless loss of life,” he said.
“How many wake-up calls does the health secretary need before he finally devises a coherent strategy to tackle the unacceptable emergency waiting times in Scotland?”