The number of ambulances taking longer than an hour to reach an emergency has more than doubled since 2000, newly released figures have suggested.
The Ambulance Service employed 412 extra staff in recent years
The statistics, obtained by Christine Grahame of the SNP, showed that 189 patients had at least an hour wait in 2005/06, compared with 71 in 2000/01.
The increase comes despite a large rise in the number of trained crews, the MSP for the South of Scotland said.
The Scottish Executive said the service saw a 30% rise in calls in that period.
Ms Grahame requested the figures after a stroke victim in her constituency reported waiting more than two hours for an emergency ambulance crew to arrive at her home.
The SNP's social justice spokeswoman said: "There is clearly something seriously wrong with the management and operational systems and these figures show the experience endured by my constituents is not unique at all."
An executive spokeswoman said: "Ambulance response times in Scotland have improved in the last year - 13,000 more calls were responded to within eight minutes.
"The average response time to category A calls is 8.4 minutes.
"The ambulance service is now dealing with roughly 30% more emergency calls than it was in 2002/03 and in order to respond to this, an extra 412 paramedics and technicians have been employed and funding has increased by 50%."
She said a priority system was introduced in 2003 which divided call-outs into life-threatening and less serious categories.
The Scottish Ambulance Service said that since the prioritisation of 999 calls was brought in, people who needed help the most were getting a faster response.
Stroke victim Agnes Alexander waited about three hours for help
Non life-threatening calls would get a response that is "more appropriate to their condition," a spokesman said.
He highlighted the 8.4 minute emergency response time as the fastest it has ever been.
Ms Grahame demanded ministers hold an immediate inquiry into why the number of delays were increasing.
She said: "This marked rise cannot be explained away by vexatious 999 calls by people who do not require emergency treatment - something far more serious is taking place.
"I remain of the view that the fault is not with individual crews, but with a management and operational structure which is failing to reach emergencies within what is widely regarded by medical professionals as a crucial first hour.
"In many cases it will mean the difference between life and death and I suspect that some deaths will have sadly occurred as a result of these delays."