Strikes by drivers at East Midlands Trains have been planned for three days during the London 2012 Olympics in a row over pensions.
Members of the train drivers' union Aslef have scheduled industrial action for 6, 7, and 8 August.
It said talks with East Midlands Trains had failed to produce a breakthrough over pension contribution cuts.
The rail operator said Aslef was "playing games" and the strikes were a "kick in the teeth" for customers.
Aslef members oppose East Midlands Trains' plans to reduce both its own and staff contributions to its pension fund from July.
Aslef's general secretary Mick Whelan said: "To cut pension contributions in the current climate is highly irresponsible."
The managing director of East Midlands Trains, David Horne, said: "This is yet another example of Aslef playing games and is a real kick in the teeth for our customers and the country during a time of great national pride."
Aslef has said it will have further talks with East Midlands Trains on Friday with a view to resolving the dispute.
East Midlands Trains had said in June that the change would leave drivers £500 a year better off without affecting pension benefits.
The firm announced on Wednesday that it would be providing 50,000 extra seats on trains to London for the games.
Industrial action had been suspended on two dates in June to allow for negotiations with the rail operator to take place.