Trains currently run every 30 minutes on a Sunday between Helensburgh Central and Dumbarton - a number which is set to be slashed - although exact details of how services will be affected are yet to be established. However, the firm has reassured customers that at this stage only Sunday services will be affected.

Scotrail insists it will providing more carriages on the trains that will run, in a bid to reduce the number of people affected by offering the same capacity.

Bus services will also be operated to keep connections to ferry services running.

The final timetable will be published tomorrow (Thursday) ahead of cuts starting from Sunday.

A dedicated web page has been set up at www.scotrail.co.uk/sundays - which will operate from Thursday - where all temporary timetables will be published alongside any other relevant information.

The firm stated the reason for the unavailability of train drivers on Sunday services was partly dependent on voluntary cover being provided by train drivers. They say the number of train drivers volunteering for Sunday work has declined, due to ongoing negotiations about pay.

Phil Verster, managing director of the ScotRail Alliance, said: “We have inherited a business that runs a seven day railway with a system of staff rostering that covers only six days. “Our customers want the same level of service right throughout the week, so we have to make changes and improve our railway. “We cannot expect our train drivers to volunteer for so many Sundays when our rosters should reflect a modern, seven-day railway for Scotland.

“We have made an offer to our train drivers that would see them get more pay, have less weekend working and have a better work/life balance.

“We do not want to reduce the number of services on a Sunday or any other day. It is not a decision that we take lightly, but we must be able to give our customers certainty about which services will be running and which ones won’t.

“We really want to get the situation resolved and we remain open to discussing our proposals and options with our unions.” The decision has been blasted by ASLEF, the train drivers’ union.