Three-quarters face being banned from proposed low emission zones (LEZs), motoring groups have estimated.
Motorists would otherwise risk fines of more than £20 a day. One in six petrol cars is also expected to be excluded from the zones, designed to cut the most harmful emissions.
The first – expected to be announced shortly for Glasgow city centre – is due to be established by the end of next year. Zones in Edinburgh, which is also bidding to be first, and Aberdeen and Dundee would follow by 2020.
Only vehicles with the cleanest engines would be permitted. They are Euro 6 diesels, introduced three years ago, and Euro 3 petrol engines, available since 2005.
Two-thirds of taxis in Glasgow and Edinburgh also have older engines, the Scottish Taxi Federation said.
The Scottish Government said grants for retrofitting taxi engines might be considered.
Bus and lorry engines would have to be Euro 6 standard, and motorbikes Euro 3. The IAM RoadSmart motoring group estimated that 738,000 diesel cars and 244,000 petrol cars in Scotland would not meet LEZ standards. Penalties have not been set, but a consultation launched by transport minister Humza Yousaf yesterday said they would be “proportionally higher” than in LEZs in other countries where drivers of vehicles not meeting emission standards were charged less than £20 a day.
That would be ten times the controversial £2 a day charge proposed for Edinburgh 15 years ago to combat congestion. The zones would operate round the clock, enforced using cameras recording vehicle number plates.
There could be exemptions for blue badge holders, emergency vehicles, bin lorries, and night shift workers when no public transport was available.
RAC spokesman Nicholas Lyes said: “These proposals will have motorists reeling at the thought that they could be banned from driving in certain areas as early as next year if they drive a diesel vehicle registered prior to September 2014.
“Motorists accept that tough measures are essential to tackle our air quality problem. However, there should not be a rush to penalise them at the first opportunity.
“Focus should firstly be on establishing which vehicles are the highest polluting vehicles doing the most mileage in the most polluted areas.
“Typically in urban areas, these tend to be buses and taxis so there must be an urgency to clean these vehicles up first.”
First Minister Nicola Sturgeon admitted the plans could be unpopular, but said air pollution in some areas of Glasgow was “really bad”.
She said: “Some of the changes that will be involved for a low emission zone… do involve behavioural change, they do involve things that can be difficult for people.
“But the scale of this challenge and the importance of this challenge means we’ve got to do these things. But if we get ahead of the game there’s also lots of benefits we can get out of this transition – we can encourage businesses to come here and do their research and make their products.”
Scottish Greens environment spokesman Mark Ruskell urged ministers to “pick up the pace” on the plans.
He said: “Traffic pollution causes lung and heart disease, and thousands of premature deaths every year in Scotland, so the fact the Scottish Government is slowly waking up to the need for action shows the benefit of consistent Green pressure on this issue.
“We now need a commitment to fund LEZs with local councils, given we have 38 pollution hotspots in communities across the country.”
Emilia Hanna of Friends of the Earth Scotland said: “The obvious place for the first LEZ is Glasgow, because it has the highest death toll from air pollution, with over 300 people dying early from toxic air each year.”
Mr Yousaf said: “This consultation will help us deliver LEZs that are well designed with consistent national standards.
“As well as improving air quality, LEZs can also contribute to tackling congestion.
“The vehicles to be included in, or be exempt from, LEZs will be for individual local authorities to decide.”
The first LEZ was introduced in Sweden in 1996 and there are now more than 250 in 15 European countries.
Glasgow City Council sustainability and carbon reduction convener Anna Richardson said: “Poor air quality is a significant public health concern and a major social justice issue for Glasgow.
“Having a LEZ will reduce congestion and help remove the most polluting diesel engines from our streets, improving the air we breathe.
“There is a wealth of evidence to show cities that prioritise those kind of improvements benefit not only from better health outcomes, but from more resilient economies and reduced inequality. That’s the goal.”
An Edinburgh City Council spokeswoman said: “We welcome the Scottish Government’s commitment to introduce LEZs and are working with their officials to discuss the potential benefits for Edinburgh.
“Tackling air pollution is a priority for the council, and we’re already addressing this through a range of projects.”