The NHS statistics, which show that just 84.6 per cent of patients in A&E are seen within four hours, are the worst since March 2018.
The number of Scots spending more than 12 hours in accident and emergency rose to 215 in the week ending November 10, with 793 people spending more than eight hours in emergency departments, and a total of 4338 waiting longer than four hours to be admitted, transferred or discharged.
Across Scotland the target of having 95 per cent of patients dealt with within four hours has not been met since August 2017.
The numbers were worst in Scotland's largest health board, NHS Greater Glasgow and Clyde, where the target was missed for almost one in five patients, with the flagship Queen Elizabeth University Hospital (QEUH) seeing almost a third of its patients spending more than four hours in the emergency department - with just 68.5 per cent seen in the target time.
The figures were published as the Health Secretary, Jeane Freeman, was quizzed by Holyrood's health and sport committee on infection control in hospitals, after it was recently alleged that two children had died in the QEUH as a result of water contamination.
They also come just a fortnight after bosses at Edinburgh's Royal Infirmary said its A&E department was having to cope with 50 per cent more patients than it was originally planned it would deal with when the hospital was built.
Ms Freeman is dealing with a catalogue of issues within the NHS, including the revelation that it could take five years for the children's ward at St Johns' Hospital in Livingston to reopen fully, the continued row over the new Royal Hospital for Sick Children in Edinburgh not yet being ready to open, and a damning cross-party report published yesterday claiming that cancer care in Scotland was in crisis.
Ms Freeman told the committee: "In terms of the inquiry, we are in the process of finalising who will lead that, with the support of the Lord Advocate and the Lord President. I hope to be able to announce who will lead the inquiry before we get to the Christmas recess."
She also said the announcement of the remit and the start date of the probe will closely follow the announcement of the chairperson, who will also have a hand in setting the terms of the inquiry.
Ms Freeman said: "As members are aware, the chair of the inquiry has a significant role in finalising the role of that inquiry so we will undertake that finalising work with him or her, then we will be able to announce the final remit and its start up date shortly after we are able to tell yourselves and parliament who will lead the inquiry."
Today Scottish Conservative shadow health secretary Miles Briggs said the blame for the NHS's problems lay with Nicola Sturgeon, and called on the Scottish Government to use, "extra funding proposed by a future UK Conservative government" to set out a long-term plan for Scotland’s NHS rather than rely on “sticking plaster solutions”.
He said: “Five years ago, Nicola Sturgeon was elected First Minister. Five years on, the Scottish NHS is lurching from crisis to crisis. Nothing symbolises her government’s failures better than the new Sick Kids Hospital in Edinburgh: over-budget and still not delivered.
“Meanwhile, higher taxes in Scotland don’t help the NHS – they just deter well qualified medical staff from staying or coming to Scotland.”
“Hundreds of millions of pounds of extra investment for the NHS in Scotland has been guaranteed by a future UK Conservative government. Rather than using this cash to buy yet more sticking plaster, it is time that SNP ministers came up with a plan that ensures we have the staff to cope with rising demand, and buildings that patients can trust”.
He said: “She can't escape the fact the SNP government hasn't met the A&E target for years. Now the number of patients waiting more than eight and 12 hours has rocketed.
“To offer patients a brighter future, staff must have the resources they need to do their job. A good place to start would be for ministers to publish the integrated workforce plan that staff were told would be out last year.
"My party also persuaded the Scottish Government to put new mental health workers in A&E, but ministers have now diluted their commitment. Liberal Democrats would create new 24-hour mental health practitioner cover in every A&E, transforming services and ensuring it is treated as seriously as physical health."
A Scottish Government spokeswoman said: "Scotland's core A&E departments continue to be the best performing in the UK and have been for more than four years despite experiencing continued high attendance levels.
"This is thanks to the ongoing hard work and dedication of our NHS staff who ensure that people get the best care possible.
"We continue to work closely with those health boards facing the greatest challenges to help drive improvements.
"To tackle the particular pressures winter brings, we have invested £10 million to help boards put appropriate steps in place to ensure quality of care, patient safety and access to services are maintained over the winter period."