Trade union leaders have rejected a 4.2% pay deal, prolonging a dispute that has seen more than 700 rail services cut.
Aslef, which represents train drivers, negotiated with the newly-nationalised ScotRail last week, with organisers securing a pay increase.
But the union’s national executive committee decided to reject the deal on Wednesday, saying members would be balloted on industrial action should the operator refuse to come back to the table.
A spokeswoman for Transport Scotland said they were “disappointed” in the response from Aslef, urging unions to look for a deal that is “both fair and affordable”.
Kevin Lindsay, the union’s Scottish organiser, said: “Aslef wants to negotiate a fair deal for our members - we are once again calling on ScotRail to return to the talks, so we can negotiate a fair pay offer that we can put to our members.”
The pay dispute has been the first major hurdle for the new ScotRail, which was brought into public ownership in April.
As a result of the disagreement, drivers refused to work on rest days, plunging the service into chaos with cancellations and delays.
ScotRail responded by putting in place a temporary timetable that saw more than 700 services cut.
A Transport Scotland spokeswoman said: “We are disappointed that Aslef, having given due consideration to the terms they negotiated, have decided to reject the very good offer on the table, an offer which is in part self-funded through increased revenue and efficiencies.
“While we understand any union’s desire to obtain the best deal possible for their members, the stark realities of the financial pressures we are facing across government are evidenced by the Spending Review published just yesterday.
“However, to be part of the vision moving forward, the unions need to agree on a deal that is both fair and affordable, particularly in the context of wider public sector pay policy.
“While, regrettably, this decision appears to mean further disruption for passengers in the immediate term, given there is no indication that drivers will return to previous rest day working and overtime arrangements, we would encourage all parties concerned to get back round the table to resume negotiations.”
Scottish Conservative transport spokesman Graham Simpson said: “Once again, train passengers in Scotland are set to suffer thanks to SNP complacency and dithering.
“Yesterday I asked Jenny Gilruth what contingency plans were in place should Aslef reject the current pay offer and she had no answer.
“Now, it appears, we’re back to square one and the Scottish public will have to endure the woefully-inadequate reduced ScotRail timetable for even longer.
“Since ScotRail was nationalised two months ago, ministers haven’t put a foot right - they must get ScotRail and the union back around the table immediately to end this chaos as quickly as possible.”
David Simpson, ScotRail service delivery director, said: “We’re incredibly disappointed and frustrated that Aslef bosses have rejected this improved pay offer. It’s astonishing that they will not even put this offer to their members.
“Our substantially improved pay offer reflects the cost-of-living challenges faced by families across the country, while balancing it against the need to provide value for the taxpayer.
“We have offered to meet Aslef but, in the meantime, would urge them to reconsider this offer in the interest of their members and the future of the railway in Scotland.”
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