Friends Of The Earth Scotland said there could be more than 3,500 early deaths from air pollution in Scotland every year, substantially more than the previous estimate of around 2,000.
The charity criticised attempts to address the air quality issue as “incomplete, vague, and lacklustre” but the Scottish Government said progress had been made.
The new figure draws on early analysis from the UK Department for Environment, Food and Rural Affairs (Defra) on the impact of nitrogen dioxide (NO2).
Defra’s draft plan for improving air quality in the UK estimates that the effects of NO2 on mortality are equivalent to 23,500 deaths annually in the UK.
Previously only estimates for the impact of fine particles, known as PM2.5, was known.
A 2010 report by the Committee on the Medical Effects of Air Pollutants concluded that exposure to these particles had an effect on mortality equivalent to nearly 29,000 deaths, or around 2,000 in Scotland.
The charity produced a Scotland estimate for nitrogen dioxide by assuming a similar impact as that from fine particles.
Friends Of The Earth air pollution campaigner Emilia Hanna said: “Air pollution is probably killing more than 3,500 people in Scotland every year, which is nearly twice as many as previously thought.
“This new health evidence is truly shocking, hugely alarming and demonstrates that air pollution is a major public health disaster.”
The Supreme Court has set a deadline for the UK and Scottish Governments to produce plans for reducing air pollution levels in order to comply with European Union (EU) law on limits for nitrogen dioxide in the air with consultations ongoing.
Ms Hanna added: “The Scottish consultation on new air quality plans is incomplete, vague, and lacklustre.
“The law requires that the low-emission strategy and related regional air quality plans have a clear set of actions to reduce air pollution, specific timetables for action, and estimates of how much each measure will improve air quality.
“When the Scottish Government launches its low-emission strategy in November, the strategy needs to fully comply with the letter and the spirit of the law.”
The charity is calling for “fully funded” low-emission zones in major cities with air pollution problems by 2018.
A Scottish Government spokesman said: “Since 1990 nitrogen oxide emissions in Scotland have fallen by 67% but further progress is required.
“Following consultation earlier this year on a low-emission strategy, the Scottish Government is working with partners such as local authorities and Transport Scotland to finalise the strategy for publication later this year.
“This will draw together in one place a range of existing and additional actions which will support delivery of further improvement in air quality, supporting individuals and communities across Scotland.”
Sarah Boyack MSP, Labour’s environmental justice spokeswoman, said: “This is a major public health risk and the toll is unacceptable. In air pollution hot spots throughout our urban areas, EU limits are regularly breached.
“We need an effective strategy from the SNP Government, which is properly funded, addresses the need for low-emission zones and includes a timetable for action.
“The response from the SNP Government looks utterly complacent. The point is that current action is not working, so telling us what is currently happening in a glossy document doesn’t cut it. We need better than that.”