The proposed changes from next May would see some 2,100 weekday trains running compared to 2,400 before the Covid crisis – or about one in eight fewer than in 2019.
However, the total is slightly more than the current 2,004 daily services, which have been reduced because of lower demand, including in the evenings.
During the pandemic they had been progressively reduced to a low of around 1,600 in January.
Scottish Labour warned that Scotland could not meet its carbon reduction targets with a “diminished” rail network, while train drivers’ union Aslef condemned the plans as “unnecessary”.
Dr John McCormick, chair of the think-tank Scottish Association for Public Transport, said: "We accept something needs to be done to reduce the ScotRail deficit, but we would prefer to see much more use made of ScotRail trains to boost revenue and cut road traffic and emissions.
“There is no point in the Scottish Government setting ambitious net-zero targets, but having no strategy to achieve them.”
The new “Fit for the Future” timetable would see many currently-reduced services continue, such as off-peak trains on the main Edinburgh-Glasgow route halved to half-hourly, and those between Edinburgh and Tweedbank in the Borders halved to hourly.
Trains between Inverness and Edinburgh would be re-routed via Stirling rather than Fife, with “no material” increase in journey time.
This would be accompanied by a shake-up of services through Fife, including hourly trains between Edinburgh and Dundee via Kirkcaldy, Edinburgh and Perth via Dunfermline, Edinburgh and Kirkcaldy via Kinghorn, and Edinburgh and Glenrothes with Thornton via Dunfermline.
However, some journey times may be “slightly increased” because trains will stop at every station rather than split some stops between them.
Through trains on the Edinburgh-Glasgow route via Cumbernauld will end.
Extra trains would run between Dundee and Glasgow to establish an hourly service.
There could also be expansion on other lines, such as for summer services on the Glasgow-Oban/Fort William/Mallaig route, where ScotRail’s longer Inter7City trains that currently run between Scotland’s cities will be considered.
ScotRail said that would not be possible without more drivers, but denied its current shortage due to retirals and training being suspended during the pandemic was a factor in not restoring other services.
In a public consultation to be launched on Friday, the operator said: “We have reviewed the timetable across the whole network to ensure that the service meets the needs of customers and the Scottish Government’s aims as Scotland recovers from the pandemic and in the future.
“We are proposing a new timetable operating around 2,100 services per weekday as the foundation to encourage a return to public transport following the pandemic.
"Most customers will find the number of calls at their station and the destinations served are similar to today.
“However, there are some areas where there is greater change.”
The operator said this was to address the large number of empty seats on several routes before the pandemic, when fewer than one in four were filled on a typical weekday.
It said: “Returning to our pre-pandemic timetable would result in our trains operating 26 million more vehicle miles each year for little customer benefit.
"As well as increased emissions, that would increase ScotRail costs to the taxpayer by £30 million to £40m each year.
"Our new customer-focused timetable will reflect predicted levels of service as well as the need to provide the best value for money for taxpayers.”
The changes follow a doubling in annual Scottish Government funding to some £1 billion to offset the reduction in income during the coronavirus crisis when passenger numbers fell by as much as 90 per cent.
They have now increased to 50 per cent of pre-pandemic levels and Saturdays has been the busiest day.
However, further restoration of weekend travel has been hampered by strikes as part of a pay dispute among conductors halting most trains on Sundays since March.
Alex Hynes, managing director of Scotland’s Railway, which comprises ScotRail and track owner Network Rail Scotland, said: “Our job is to keep people moving and connected to business, leisure and education while meeting the expectations of our customers.
“The pandemic has changed how people travel across all of Scotland, so our services will reflect these varied travel patterns and deliver timetables that are reliable, have enough capacity to meet pre-Covid levels of demand and are sustainable.
“We are consulting on the timetable changes being proposed and we would welcome the views of our customers.”
ScotRail operations director David Simpson added: “The significant cost of running the railway following the impact of the coronavirus pandemic means it’s essential that the railway meets the changing needs of customers, as well as provides the taxpayer with best value for money.
“Our timetable proposals do that.
“That might mean offering a different service on different days of the week or different times of year as passenger demand varies across the week or through the year.
"But by doing so, we can ensure Scotland’s Railway remains sustainable into the future.”
But Scottish Labour transport spokesperson Neil Bibby said: "We cannot build back from the Covid crisis or meet Scotland’s net-zero ambitions with a diminished rail network.
“ScotRail is due to enter Scottish Government ownership next year.
"It would be astounding if the first act of the Scottish Government when taking ownership of ScotRail was to implement major cuts to rail services and jobs.
"The transport minister must set out his position urgently.
“The SNP and the Greens cannot credibly claim to be leading the country’s response to climate change when massive cuts to rail services are on the table.
“Passengers and staff will not support cuts like this to the rail network and their voices must be heard.”
Graham Simpson, his Scottish Conservatives counterpart, said: “Rail users will be shocked by the scale of these proposals and I'd encourage them to make their views known.
“As we rebuild from the crisis, we want more people to use public transport.
"There is a real danger that some of these cuts will force people into their cars instead.
“Significant money was given to ScotRail during the pandemic and these potential cuts must not now be a direct result of SNP ministers wanting to claw back some money.”
Kevin Lindsay, Aslef’s organiser in Scotland, said: "I’m sure rail passengers and workers will stand up to these unnecessary cuts.
"If the Scottish Government is serious about reducing Scotland’s carbon footprint, then it needs to be clear that there will no cuts.”
A sustainable transport expert added: “Ministers have a commitment to decarbonise transport and the railway has an important role to play in this.”
Robert Samson, stakeholder manager for passenger watchdog Transport Focus, said: “The significant improvement in punctuality achieved over the last year must be maintained in the proposed timetable.”
Colin Howden, director of sustainable transport campaigners Transform Scotland, said: “The recent paper by Professor Iain Docherty highlighted the multiple pressures facing the railway.
"These include the escalating cost of running services, many more people deciding to continue working from home, and damaging government messaging telling people to avoid public transport.
“We’d like to see all cost savings ploughed back into improving rail infrastructure.
"It’s going to be difficult to get significantly more people travelling by rail until train services can provide journey times competitive with road.
"The Scottish Government has spent billions on speeding up the inter-city road network whilst leaving most of our inter-city rail routes with infrastructure which would still be familiar to the Victorians."
Transport minister Graeme Dey said: “Organisations up and down the country are reflecting on how they can provide great customer service while at the same time ensuring their businesses are fit for the future.
"Rail is no different and that is why it is essential ScotRail review changes in travel patterns across Scotland so that timetables best meet demand.
“This consultation exercise offers an opportunity for customers and businesses to help shape a reliable and responsive timetable change from May 2022.”