Rail union RMT announced further action was being planned as part of an ongoing industrial dispute that has lasted for eight months.
The organisation confirmed conductors and ticket examiners striking alongside colleagues throughout COP26 after the union vowed to continue strike action on Friday.
A formal written offer was made to all four rail unions two weeks ago, but RMT confirmed that they would be continuing strike action despite the offer.
RMT general secretary Mick Lynch confirmed that further action was being considered by RMT.
In a statement, he said: "Our members are standing firm across Scotland again this morning in this on-going fight for pay equality and workplace justice. Due to the hard-headed attitude of ScotRail, we have had no option but to confirm further strike action by our ticket examiner members right through to the new year.
"It is disgraceful that the SNP have decided this weekend to launch unprecedented attacks on Scotland's rail workers, who have kept the country moving throughout the pandemic and now find themselves under assault from the political elite.
"It's about time those calling the shots in Scotland took responsibility for Britain’s longest running industrial dispute, which is over the basic issue of pay equality on Scotrail. With COP26 looming large it's time to settle the whole raft of disputes on our railways which shame Scotland.
"There is still a window of opportunity to reach a negotiated settlement to the on-going disputes on both Scotrail and the Caledonian Sleeper and RMT stands ready to meet anytime, any place anywhere."
Ian McConnell, ScotRail’s chief operating officer, said: “I’m disappointed and incredibly frustrated that RMT representatives have point blank rejected our latest proposal.
“The RMT leadership, despite stating that the only matter needing to be resolved was rest day working, have now moved the goalposts without consulting their members. It can only indicate they’re not serious about moving forward and delivering a successful COP26.
“Time is now running out to reach agreement and, despite a pay offer of 4.7 per cent over two years, a £300 payment for COP26, and a rest day working enhancement, it seems RMT bosses are intent on sabotaging Scotland’s Railway’s role during COP26.
“With the threat of industrial action remaining, we’re continuing to develop contingency plans to provide a core service for the duration of the summit.”
The Scottish Government has been approached for comment.