Figures released yesterday show only 86.9 per cent of patients were seen within four hours last week, well below the 95 per cent target and the lowest since March 2015.

NHS Lothian had the worst figures with 77.3 per cent seen within four hours, falling to just 64.1 per cent at the flagship Edinburgh Royal Infirmary.

Ministers have now been forced to send in a team of Scottish Government officials to work with the health board to improve the dire situation.

The report showed 107 patients waited more than 12 hours in Accident and Emergency last week, most of them in Lothian or Lanarkshire, with 450 waiting more than eight hours.

Meanwhile, the collapse in A&E waiting times came as another new report revealed the number of hospital beds in Scotland has fallen again, to 21,246, down more than 2,000 on five years ago.

With the winter flu season now in full swing, Ms Robison appeared to suggest casualty departments had been unable to cope with icy conditions seen across much of Scotland as well.

In fact, A&E wards dealt with 25,840 patients last week, which was down slightly on the previous week and more than 2,000 fewer than the busiest week of the year so far when 27,879 patients were seen in June.

She said: “Cold weather and particularly black ice is affecting the performance of our A&E departments and, while we expect waiting times to fluctuate from week to week in winter, there is no doubt that slips and trips and flu-like illnesses have significantly increased the pressures on our hospitals recently.

“What remains a constant is the dedication of staff across Scotland’s healthcare system who should get the praise they rightly deserve for their hard work.

“Boards are working hard to mitigate against the biting effects of winter. The funding I announced last week will ensure additional staffing and capacity are being made available to build resilience across the whole system and it will take a few weeks for the benefits to work their way through the system.

“We are specifically working with NHS Lothian to help identify and provide solutions to improve flow through the hospital, which in turn will boost its performance and improve waiting times for patients.”

In response to her statement, Scottish Tory shadow health secretary Miles Briggs tweeted: “Well this is a new excuse from SNP Ministers. Nothing to do with SNP mismanagement of our NHS workforce of course and the cuts to A&E beds. Many A&E units across Scotland have been in winter crisis management for months.”

He added: “SNP ministers have repeatedly boasted about A&E performances but these figures will give them nothing to crow about.

“The systematic failure of the Scottish Government to invest or support primary care has led to a predictable displacement of patient activity, driving up waiting times in emergency departments.

“The sad reality is that emergency departments cannot cope with this increase in patients, as well as seasonal pressures, so patients are waiting longer, many of whom are in serious discomfort.”

Mr Briggs went on to describe waiting times in the Lothians as “particularly bad” and called on the health board “to reduce them as a matter of urgency”.

Hairmyres Hospital in Wishaw had the second worst performance, with 74.1 per cent of patients seen within four hours, followed by Queen Elizabeth University Hospital in Glasgow and Royal Alexandra Hospital in Paisley – both with 81.2 per cent.

Scottish Labour health spokesman Anas Sarwar MSP said: “These figures are a nightmare before Christmas for the SNP and Health Secretary Shona Robison.

Our doctors and nurses do fantastic work, but they have been left over-worked, under-valued and under-resourced by this SNP government.

“Almost 20 hospitals failed to hit the A&E target last week, leaving hundreds of patients stranded in hospitals for more than four hours.

The number of acute hospital beds has also fallen by more than two per cent.

“This is a disgrace and it is clear Scotland could now be facing an A&E winter meltdown under the SNP.”