A reduced temporary timetable is being introduced on ScotRail trains from tomorrow.
The train operator said the service cuts are needed because fewer train drivers are available for overtime due to a dispute over pay.
ScotRail said the new timetable will provide “certainty” over what trains will run while the union says the bosses should be negotiating a fair deal for drivers instead of cutting services for passengers.
The reduced timetable will start on Wednesday with changes to the first and last trains on a number of routes and a reduced frequency throughout the day on many services.
It comes after Aslef, the train drivers’ union, recommended a ballot on industrial action.
ScotRail said over the past number of weeks, it has been in pay discussions Aslef, RMT, TSSA, and Unite.
A formal pay offer in line with the Scottish Government’s public sector pay policy was made on Friday, July 5, which was rejected by all four trade unions.
Full details of each service are available on the Scotrail website
Mark Ilderton, ScotRail service delivery director, said: “We are very sorry to customers for the disruption to services. We know that customers want certainty and reliability, which is why we are introducing a temporary timetable, in place of late-notice cancellations.
“We are operating services which the vast majority of customers use and are still using all the available trains in our fleet so customers can continue to travel.
“We want to resolve the pay dispute with the trade unions and remain fully committed to further discussions.
“We’re asking customers to check their journey on our website or mobile app, as train times will have changed.”
Aslef said ScotRail must invest in its workforce.
Kevin Lindsay, Scottish organiser, said: "Rather than slashing the timetable in an act of economic vandalism that will impact towns and cities across Scotland as well as Scotland's rail passengers, ScotRail and the Scottish Government must get serious about pay and urgently get back round the negotiating table with a serious and credible offer.”
The union said the latest offer was “completely unacceptable”.
Lindsay added: “The Scottish Government and ScotRail need to understand quickly that investment in our railways includes investing in its most precious resource, its workers. We urge them to come back to us with an offer that is serious and that treats our members with the fairness and respect they deserve."
ScotRail said is currently recruiting 160 new drivers each year to improve resilience, but that some rest day working and overtime is still needed to deliver a normal timetable.
It said this has historically been the case in the railway and is replicated in other train operators across Britain.