Staff at Doncaster train operator walk out in 24-hour strike over jobs and conditions
The Rail, Maritime and Transport union suspended industrial action in the summer but the long-standing dispute remains unresolved.
RMT general secretary Mick Cash said: "RMT will not sit back while nearly 200 members' jobs are under threat and while conditions and safety are put at risk by a franchise which is clearly in financial trouble.
"The union suspended an earlier programme of action when it looked like serious progress was being made in talks, but that process has now failed to reach a satisfactory conclusion and we are back into industrial action as a result.
"We have been shocked at the way the company have led us up the garden path when we entered talks in good faith. Our representatives are rightly angry at this cavalier approach."
Virgin Trains said it will run a full timetable during the strike.
The company said it was making changes to customer-facing roles which will see a single person take responsibility for the "customer experience", adding: "This will have no impact on safety, and will result in a better experience for customers.
"Virgin Trains has also given assurances on each point raised by the union at the start of the dispute - such as ruling out any compulsory redundancies as a result of the changes."
David Horne, managing director for Virgin Trains on the East Coast, said: "We have worked hard to ensure there are comprehensive contingency plans in place and I want to reassure our customers that our timetable will be unaffected during these walkouts, as well as during any subsequent strikes by the RMT.
"The changes we are making are part of the customer-centric revolution we have planned for the East Coast. We're already more than halfway through our complete refresh of our trains with all new interiors being rolled out, and in two years will have our brand-new Azuma trains coming into service.
"Alongside more modern trains, we want a modern customer service proposition - one that focuses firmly on the customer.
"With our guarantees that there will be no compulsory redundancies, no impact on safety and a full timetable in place during the walkouts, these strikes will cost RMT members pay for no reason, and we urge the union to rejoin us around the negotiating table."
The RMT said in a statement: "The ongoing dispute initially came to a head as the company chose to ignore the agreed negotiating machinery and subjected staff to a barrage of direct propaganda justifying their attempts to bulldoze through a package of cash-led measure that would decimate jobs, working conditions and threaten the safety regime that currently ensures a guard on every train.
"Nearly 200 jobs across the franchise are threatened by the cuts. Those staff remaining will be expected to cover the work of the deleted posts, piling intolerable pressure on all sections of the workforce."