Train managers on FirstGroup PLC's (LSE:FGP) Avanti West Coast mainline have voted to go on strike on New Year’s Eve and every subsequent Sunday from 12 January until 25 May.
Strike action was planned for the Christmas period but was postponed after a new offer from Avanti, but this has now been rejected by the train managers.
A statement from the RMT said that "sustained strike action" was now "the only way to focus management's minds on reaching a negotiated settlement".
Avanti West Coast, a joint venture between FirstGroup and Italian group Trenitalia, said the strikes would cause "significant disruption" to customers of the service that runs from London to Glasgow
RMT said 83% of its members involved in the dispute, which is over payments on rest days, voted against the new offer.
Avanti said it was "disappointed" by the vote but remained "open to working with the RMT to resolve the dispute."
Rail services in the UK have been disrupted for more than two years by a raft of disputes over pay, conditions and work patterns.
The Labour government intends to renationalise the railways to end the disruption with South Western, c2c and Greater Anglia the the first three routes to be taken back under state ownership.
Shares in FirstGroup edged up 0.4% to 165.2p.