Rail services in Sussex will be hit when workers for South West Trains stage two 48-hour strikes.
It is likely to mean no trains on the service between Brighton and Reading via Chichester and Basingstoke.
South West Trains runs six trains, Monday to Friday, on the route.
Members of the Rail Maritime and Transport Union, including guards, plan to walk out on January 3 and 4 and January 7 and 8, after rejecting a pay deal worth 3.8 per cent.
In past years, any industrial action by staff at the company has badly hit services out of Brighton.
The action was announced by Vernon Hince, the union's acting general secretary.
He said his members were "incensed" at the way they had been treated by the train operator.
The union rejected a 3.8 per cent pay offer, after train drivers belonging to the union ASLEF were given a better deal.
The RMT said there had been a three-to-one vote in favour of a strike over pay in a 70 per cent turnout of its 2,000 members at South West Trains.
Mr Hince said: "Our members have stated loud and clear they expect equal treatment.
"All we are demanding is a fair deal for all staff.
"Why should non-driver employees be treated less favourably when they work every bit as hard and are equally loyal?"
RMT train crew members have also voted for industrial action in a separate dispute over disciplining of two union members.
The union will decide its next moves before Christmas.
South West Trains said it was "bitterly disappointed" for its passengers.
A spokesman said: "We felt that by offering independent arbitration on pay we were suggesting a sensible way forward which would have allowed the RMT to make its case without inconveniencing our passengers.
"They have chosen to go down the route of disruption."
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