Train managers on Avanti West Coast services are set to strike for five months, starting New Year’s Eve, in a dispute over rest day working.The Rail, Maritime and Transport union (RMT) announced the industrial action will affect West Coast Main Line services between London, the North West and Scotland.The strikes will begin on December 31 and continue into spring 2024.The industrial action will take place on December 31, January 2, and every Sunday between January 12 and May 25.Avanti commuters face five months of strike ‘disruption’ as RMT stage walk-out just days after Britons avoided Christmas chaosPAThe decision follows an overwhelming rejection of Avanti’s latest offer by RMT members, with 83 per cent voting against the deal on a turnout of 82.9 per cent.The strikes were originally planned for December 22, 23 and 29 but were called off after a revised offer, which was subsequently rejected.Avanti West Coast expressed disappointment over the strike action, warning it would cause “significant disruption” to customers over an extended period.”We’re disappointed our train managers who are RMT members have voted to decline the very reasonable revised offer made to them to resolve the rest day working dispute and avoid inconveniencing our customers,” a spokesman said.An Avanti West Coast trainPAThe company stated it remains open to working with the RMT to resolve the dispute.An RMT spokesperson said: “Our members have resoundingly rejected Avanti’s latest offers in two referendums and sustained strike action is now the only way to focus management’s minds on reaching a negotiated settlement with the union.”Philip Haigh, a former deputy editor of Rail magazine, suggested the RMT was “playing hardball to force a more generous offer from the Government which controls Avanti spending.”Avanti West Coast’s performance has been notably poor, with just 41 per cent of trains arriving on time during the three months to September, according to Office for Rail and Road statistics.An image from the RMT picket lineGB NewsThis makes Avanti the worst-performing train company in Britain for punctuality, falling well below the national average of 67 per cent.Earlier this year, former transport secretary Louise Haigh threatened to nationalise Avanti over its poor performance, though this did not materialise after the company claimed it had “worked hard” to improve punctuality.The dispute centres on convincing train guards to work on their rostered rest days, including Sundays.A “new technology payment” linked to scanning electronic tickets is also part of the negotiations.Last week, union bosses instructed train guards to stop using company ticket scanners until further notice, as part of what Avanti sources described as a separate dispute from the rest day working discussions.