Rail workers are to be balloted for strikes in a row over extra payment for working during the Olympic Games.
Members of the Rail Maritime and Transport union at Greater Anglia, which includes the Stansted Express, will vote on whether to take industrial action.
The union said proposals from the company for Olympic payment arrangements were "divisive and wholly inadequate."
General secretary Bob Crow said: "Greater Anglia have deliberately dragged their feet over this crucial issue, knowing that the clock is ticking down and they have now confronted us at the 11th hour with an offer which they knew full well would be totally unacceptable.
"As a consequence, we now have no option but to move to an urgent ballot for both strike action and action short of a strike to reinforce our case for a fair and unified settlement.
"There can be no excuse for the cavalier attitude of the company to these negotiations on an essential section of the Olympics transport network and we would hope that they would now come to their senses and enter into meaningful talks at this late stage."
A Greater Anglia spokesman said: "We're surprised to hear that the RMT are intending to organise a ballot as we have not received any formal notification from the union of their intention to do so.
"We will continue to progress the constructive discussions that are taking place over this matter with the RMT and our staff representatives."
No details were given of what the company has offered the union, which has struck deals with several transport firms for extra payment during the Games.
Thousands of bus workers are set to strike on Friday in pursuit of a claim for a £500 Olympic payment, threatening travel chaos in the capital.