ScotRail is to introduce a temporary timetable on weekdays from May 23, with another new weekend schedule to be announced.
ScotRail claims the changes are due to pay disputes with unions after passengers faced "more cancellations than is acceptable".
The operator says it relies on drivers working overtime or on rest days, "like many other train operators across Britain", but many drivers are refusing to comply.
Hundreds of services have been cancelled this month as the train operator called the current level of cancellations "not sustainable" for customers and colleagues.
Its announcement said: "From Monday, 23 May, ScotRail will introduce a temporary timetable to provide greater certainty and reliability for customers.
"This is a result of the ongoing impact of a significant number of drivers declining to make themselves available for overtime or rest day working, following an announcement by the drivers' union ASLEF that it will ballot for industrial action over pay."
The company, which moved into public ownership in April, committed to phase out its reliance on this practice in 2019, but blamed the pandemic for significantly delaying driver training.
ScotRail is drawing up temporary timetables for weekends that will be announced in the coming days.
The new Saturday timetable is said to be broadly similar to the temporary weekday schedule.
David Simpson, ScotRail Service Delivery Director, said: "We are very sorry to customers for the disruption of recent days. We know what customers want more than anything is certainty and reliability, which is why we are introducing a temporary timetable.
"We want to resolve this dispute with the trade unions and move forward together to provide the safest, greenest, and most reliable railway we can for Scotland. We remain open to further talks with the trade unions.
"We're asking customers to check their journey on our website, mobile app, and through our social media channels as train times will have changed."
The new temporary timetable can be viewed on the Scotrail website here.
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