'Very few' Northern trains on Saturdays in December
Northern will run less than a third of its services on Saturdays in the run up to Christmas, with "very few" trains in the evening.
Passengers in the north of England will face major disruption during the latest round of strikes on 8, 15, 22 and 29 December.
One tweeted that the recent service offered by the operator had been "absolutely shambolic".
RMT members are embroiled in a lengthy dispute about train guards.
The Department for Transport (DfT) urged members to call off the "needless" industrial action.
Northern said it will run about 700 trains on each of the strike days - just under 30% of its normal service - with "very few trains" after 17:00 GMT.
It is likely to affect those visiting the Christmas market in Manchester, as well as those travelling for football matches and concerts in other major cities including Liverpool, Leeds, Huddersfield, Newcastle and Sheffield.
Engineering works are also taking place, affecting trains at Bolton and Wigan.
Passenger Stephanie Williams tweeted that Northern's services in the last three years had been "absolutely shambolic and totally unacceptable".
Jane Brazzill tweeted: "So much for being able to visit the Christmas markets - we have no train services at all on Saturday from Irlam to Manchester."
Transport for the North, which manages the Northern franchise with the DfT through the Rail North Partnership, said it backs the union on maintaining a second member of staff on trains.
But it called on the operator and the RMT to "begin meaningful discussions as soon as possible" as passengers "need reliability".
Its chief executive, Barry White, said: "Businesses across the north... are reaching their busiest time of year.
"Christmas markets are transforming our bustling centres and people want to enjoy all our economies have to offer.
"But this is being hampered by uncertainty and disruption on the rail network."
Events likely to be affected:
Manchester's Christmas markets, with no Northern services to Liverpool, Warrington Central, Kirkby and Rose Hill Marple.
- Huddersfield Town v Brighton & Hove Albion
- Sheffield Utd v Leeds Utd
- Blackburn Rovers v Sheffield Wednesday
- Mumford and Sons at First Direct Arena, Leeds
- Star Wars: A New Hope in concert at Manchester Arena
- Jeff Wayne's War of the Worlds, Metro Radio Arena, Newcastle
- Magic of Motown, Echo Arena Liverpool
The DfT has pledged its support for a second staff member on trains and added: "We believe this commitment should ensure that the needless RMT industrial action on Northern comes to an end."
Northern said it "welcomes the commitment" from the government and TfN and there was "no reason" for the RMT to continue striking.
RMT general secretary Mick Cash said: "We thank the public for their continuing support and understanding. These disputes are all about safety and passenger service on Britain's increasingly violent and dangerous railways."
He said the union "awaits any new proposals" from Northern which maintain "the same level of safety, security and access that they enjoy at the moment based on the guarantee of the guard on every train."
Earlier this month Northern said leaves on tracks and strikes had caused its worst punctuality figures for over two years. It follows timetable "carnage" over the summer, which saw the firm cancel 165 daily services.