The number of patients forced to wait too long to be seen in accident and emergency departments nearly trebled in five years.
A government watchdog found that around 104,000 people waited longer than the four-hour target in 2012-13, up from 36,000 in 2008-09.
The proportion of patients seen within the target fell from 97.2% in December 2009 to 93.5% in the same month last year.
The Audit Scotland findings were held up by opposition parties as evidence of failed SNP policies.
The Scottish Government said improvements have been made since the introduction of a £50million action plan last year.
In April last year the Scottish Government introduced an interim target that 95% of patients should be seen within four hours by the end of September 2014. It was brought in as a stepping stone towards a 98% target which was being missed.
According to Audit Scotland, only the Royal Aberdeen Children’s Hospital and the Gilbert Bain Hospital in Lerwick in Shetland met the 98% target each month of the 2012-13 financial year. Most others hospitals failed every month.
Auditor General for Scotland Caroline Gardner said: “Delays in A&E can be a sign of pressure across health and social care.
“While there has been improvement in performance, such as the progress made in tackling the longest waits in A&E, performance against the target still remains lower than it was when we last reported.”
Tory health spokesman Jackson Carlaw said: “This report makes it perfectly clear that a lack of staff is one of the reasons departments struggle, and it’s notable that the Scottish Government began slashing numbers about the same time casualty performances began to decrease.”
Hugh Henry, convener of Holyrood’s public audit committee, called the findings “extremely worrying”.
“The fact that things are getting worse should give cause for concern, not just for the Scottish Parliament but for the wider public,” he said.
Health Secretary Alex Neil said that, since the action plan was introduced, there had been an 87% reduction in patients waiting more than 12 hours, while performance against the four-hour target improved by 3.2% over the last year. “I am under no illusion that we have more to do and I am clear that health boards must continue to prioritise this vital work to ensure that we can build on the progress made,” he said.
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