Statistics released to the Scottish Tories under Freedom of Information found that 1,878,727 calls to both the non-emergency and emergency numbers were discontinued between the beginning of 2018 and November last year.
A discontinued call, Police Scotland say, is where a caller hangs up before speaking to an adviser.
The vast majority of abandoned calls were seen in the non-emergency number 101, with the pandemic appearing to have a severe impact on the number of calls which ended before callers were able to speak to staff.
But the number of calls waiting more than two minutes for a 999 to be answered has increased by more than 17 times between 2019 and 2020.
In 2020, the first year of the pandemic, the number of discontinued calls rose from 284,239 to 919,790.
Some 590,279 callers hung up before speaking to anyone between the beginning of 2021 and November of that year.
The number of discontinued calls to 999 remained fairly consisted in the last three years, following a rise of just over 1,000 between 2018 and 2019.
In 2019, 4,619 callers hung up, compared with 4,723 in 2020 and 2,827 up to November 2021.
However, the number of calls which took more than two minutes to be answered rose drastically in 2020.
In 2019, just 150 calls took more than 120 seconds to be answered, but just a year later that figure had risen to 2,624 – an increase of more than 17 times.
Some 2,827 calls to 999 were logged as taking longer than two minutes to be answered up to November 2021.
Scottish Tory justice spokesman Jamie Greene described the figures as “absolutely staggering”.
“Our officers are doing their best under severe pressure, but they are simply not being given the resources they need by the SNP Government,” he said.
“This situation is completely unacceptable and unsustainable going forward. We cannot have this huge volume of calls from members of the public going unanswered when they could be alerting police to serious incidents.”
Mr Greene alluded to the case of Lamara Bell, who died after police took three days to respond to calls of a crash near Stirling in 2015.
The driver of the car, John Yuill, died in the initial collision, but Ms Bell survived and was taken to hospital where she died four days later.
“We have seen tragedies occur before in Scotland when calls have been missed,” the Tory MSP said.
“These figures must be a wake-up call for SNP ministers to guarantee officers can answers calls as promptly as possible. If not, this could again have devastating consequences.”
And he called for greater funding for Police Scotland.
Mr Greene said: “These statistics are a damning indictment of the SNP’s failures to fund our police.”