Caledonian Sleeper staff are going on strike after “last-ditch talks” over fatigue and safety issues collapsed.
Services on the Scotland-London route have been now been cancelled this weekend.
Rail union RMT blamed negotiations breaking down on a “pig-headed approach” from train operator SERCO.
Members will strike between Sunday, October 4 and Tuesday, October 6 and Sunday, October 11 to Tuesday, October 13.
Each three-day strike will begin and end at 5.30pm, while members will also refuse to do overtime on other dates.
An RMT statement said: “As a result of the companies point blank refusal to engage in serious talks over the fundamental issues of fatigue and safety all action now goes ahead as planned and all services have been cancelled.
“RMT has made it clear that they have been prepared to negotiate from the outset and have been prepared to engage with ACAS while the company have tried to keep the whole process in-house rather than exploring every option to broker a settlement.
“That pig-headed approach has been key to the failure of talks yesterday which RMT entered in good faith.”
RMT said SERCO failed to provide enough rest for workers, while fatigue experienced by employees has not been addressed.
General secretary Mick Cash said: “RMT members on SERCO Caledonian Sleeper are absolutely determined to seek justice in this dispute and I know that this will be displayed by full support across the service for this industrial action.
“We had a chance to broker a settlement yesterday but SERCO have blown it.”
A statement on the Caledonian Sleeper website said: “Due to the strike action by RMT members, all Caledonian Sleeper services will be cancelled on Sunday 4th and Monday 5th October 2020.”
Ryan Flaherty, Serco’s Managing Director for Caledonian Sleeper, said: “We are deeply disappointed and frustrated that this action is going ahead at a time when everyone’s focus should be on maintaining vital Scottish transport links. Consequently, we have decided to cancel our services on the evening of October 4 and 5.
“We are in the process of contacting guests to inform them and apologise and they will, of course, receive a full refund.
“This action is completely unjustified. Less than a third of our workforce voted in favour of industrial action and our employees working on board the trains have received full pay during the pandemic, despite working reduced hours.”
“When some of our employees raised concerns about fatigue, we brought in an independent fatigue specialist to conduct a fatigue risk assessment on our services. He has completed his Report which clearly concludes that not only is Caledonian Sleeper operating within all regulations, but that only two people raised the issue of additional rooms for hosts, which has become the RMT’s main demand. It is therefore extremely disappointing that we currently remain in a position of being unable to resolve the dispute on a subject that only two people raised during the fatigue risk assessment process.
“Despite the findings of the Report and our offer to continue to engage with ACAS, which still stands, the RMT has refused to engage in negotiations to bring this dispute to a resolution, unless their unreasonable demands for rooms for every host are met.
“We remain fully committed to finding a resolution to the dispute and continue to be available for meaningful discussions to take place.”