Last year, there were 100 hours when no ambulance was available for dispatch in the city of Winnipeg.
That was up considerably from 2011, when the total was 56.5 hours.
Manitoba's Progressive Conservatives released the figures Friday, citing the results of a freedom-of-information request.
The Tories said the results show the Selinger government is playing "Russian roulette" with the lives of Manitobans.
The absence of ambulances to respond to emergencies, referred to as Code Red, is caused largely by extraordinarily long waits endured by paramedics in transferring patients to emergency rooms upon arrival at hospital. On average, that wait is now about 75 minutes.
While paramedics sit, waiting to transfer patients to emergency rooms, they are unable to take calls.
Progressive Conservative Leader Brian Pallister accused the government Friday of being complacent on the ambulance-wait issue. Pallister said Health Minister Theresa Oswald, under questioning in the legislature over the past year, has promised to fix the problem on at least two occasions, but has failed to make any progress. In fact, the situation has become worse.
"The NDP system is failing. Code Red complacency is not acceptable," Pallister told a press conference.
About an hour later, Oswald blasted the Tories, accusing them of "fear-mongering."
She said Winnipeg's ambulance response times -- at an average of seven minutes per call -- are among the best, if the not the best in the country.
She assured Manitobans that when they need an ambulance, one will be there.
"If you listen to what (the Tories) say and you're a senior citizen, you can become very frightened," Oswald said.
She said "99 per cent of the time" ambulances are ready to respond to a call, and if they're not, firefighters are. Without providing examples, she suggested Code Red periods were seconds in length -- not several minutes or longer.
Oswald allowed that wait times to transfer patients from ambulances to hospitals have risen over the past year, but said the government and the Winnipeg Regional Health Authority are putting measures in place to bring those times down.
According to information obtained by the Conservatives, the total time in a given month last year when there were no ambulances available for dispatch varied from about five hours to more than 14 hours (in December). Last June, no ambulances were available for a total of 12 hours.
There was no immediate information available Friday on the length of a typical Code Red or what was the longest period without service.
Jodi Possia, chairwoman of the Paramedic Association of Manitoba, said long waits to unload patients at hospitals are an issue across the country. She said it likely played a role in the December death of an 87-year-old Toronto woman, who waited three hours with abdominal pain for an ambulance to arrive. The circumstances surrounding the woman's death were made public this week.
Possia said the problem is not restricted to large cities. Her members report ambulances can wait for hours to transfer patients into Selkirk and District General Hospital.
"I hear from paramedics who are working in that area frequently that they are in exorbitant delays," she said. "Selkirk hospital has a crisis of its own."
Possia said her organization has no information on the length of a typical Code Red in Winnipeg. The Winnipeg Fire and Paramedic Service could not immediately be reached for comment on the issue late Friday.