Southern rail has branded a decision by drivers' union Aslef to half its number of strike dates as a "cynical ploy".
The train operators were planning to walkout for six days from 9 January in a row over the future role of rail guards on the franchise.
But the drivers will now strike on 10, 11 and 14 January. The news broke just a day after the parties held talks at mediation service Acas, which adjourned without a deal.
"This is a cynical ploy to minimise the impact on Aslef drivers' pay packets and maximises misery, disruption and hardship for passengers," a spokesperson for Southern said.
"Aslef's move shows pure contempt for the travelling public and it still causes massive disruption over next week.
"These strikes are pointless and they should call the whole thing off and let common sense prevail."
But Aslef has argued that its walkouts, which left 300,000 commuters stranded in December, are over safety concerns since Southern drivers will have to close and open train doors without the help train guards in the future.
The drivers will instead use CCTV cameras under Southern's modernisation plans. The dispute has also seen industrial action from conductors, represented by the RMT union.
"We are taking a longer-term view of this trade dispute. The company has not been prepared to move – it is simply going through the motions, turning up at Acas, as it did yesterday, and telling us that it intends to impose DOO [driver-only operations]," said Mick Whelan, general secretary of Aslef.
"We remain committed to a negotiated settlement, as was reached with ScotRail, but it is difficult to negotiate with people who are not prepared to be flexible.
"We still believe a deal can be done but we are, at the moment, a long way from that position. It is time for the company to come up with a genuine offer rather than carry on posturing."
Londoners also face a 24-hour walkout from station staff on the Underground from 6pm on 8 January.
Transport for London bosses are in talks with the TSSA and RMT unions at Acas on Wednesday in a bid to avert the strike. The protest is part of a long-running dispute over staffing levels on the Underground.
UPDATE (12:40 GMT): Aslef has announced three new strike dates.
- Tuesday 24 January
- Wednesday 25 January
- Friday 27 January