Train drivers' union Aslef will decide on Monday whether to ballot members for a strike or work-to-rule that would wipe out all ScotRail Sunday services.
It comes as passengers complained of waiting hours for trains as a shortage of drivers forced ScotRail to cut its Sunday services by a third.
A second weekend of disruption looms unless the deadlock over pay between the operator and train drivers' union Aslef can be broken in the coming days, with little sign of either side backing down.
Kevin Lindsay, Aslef's Scottish organiser, said there were no plans to hold talks with ScotRail this week, but that he remained "ready, willing and able" to consider a revised offer.
Train drivers have rejected a 2.5 per cent pay rise tied to productivity and a one-off £500 bonus, amid concerns that new Dutch franchise-holder, Abellio, is planning to cut conductors and move to a seven-day working week.
At present, train drivers work Monday-Saturday with Sunday shifts paying overtime.
However, the ongoing dispute has led to a "steep decline" in drivers volunteering to work Sundays.
Mr Lindsay said the union's executive committee would decide today on balloting members for a strike or action just short of a strike.
He said: "It would effectively mean a ban on overtime, so there would be no trains at all on a Sunday."
As the first Sunday of cutbacks told hold yesterday, passenger took to Twitter to complain. Ross McFarlane said he faced a four hour wait for the next train after ScotRail cancelled the 4.23pm service from Burntisland "due to crew member unavailable".
Joanna Grant said she and 12 friends had been left stranded in Stirling after an Inverness train was "cancelled within 30 minutes of departure". Others complained of cramped conditions and having to pay for taxis instead.
The disruption comes as commuters in the Central Belt already face a reduced service and lengthy diversions between Glasgow and Edinburgh due to six weeks of major engineering works at the Winchburgh Tunnel.
Abellio guaranteed no compulsory redundancies when it was awarded the 10-year contract to run ScotRail. However, unions, including Aslef and the RMT, have accused bosses of "redundancy by stealth" after it wrote to engineering, clerical, management and traincare staff inviting them to resign through the voluntary leavers scheme, which guarantees 70 per cent of salary regardless of length of service.
An spokesman for Abellio ScotRail said its "door remained open" to Aslef. He said: "We have tabled an offer that delivers higher pay, less weekend working and a better work/life balance to our drivers. It also means that we can deliver a robust service on a Sunday and gives us the opportunity to grow those services in the future. We believe that this is a fair offer and we remain open to discussing it with the unions."
Meanwhile, ferry services face renewed disruption with CalMac and Argyll Ferries crews planning a 24-hour strike on Friday.
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