RMT will ballot Eurostar International staff for a potential strike ahead of the Paris Olympics and Paralympics.
The union is considering the action over “fair and equal payments” for work during the games, which will be staged from July 26 to August 11. The Paralympics will be August 28 to September 8.
RMT (National Union of Rail, Maritime and Transport Workers) has not confirmed when potential action could be but has not ruled out a strike during the Olympics.
“The decision follows the company's failure to meet the union's demands for equitable compensation during the major sports event,” a statement on Friday read.
All RMT members at Eurostar International will be balloted for industrial action, including a potential strike and action short of a strike in the form of an overtime ban and no rest day working. The ballot will close on July 11.
RMT will also write to Eurostar contractors Mitie, Churchill, and Rail Gourmet, demanding they match any proposed Eurostar payments.
RMT general secretary Mick Lynch said: "Eurostar workers deserve fair and equal payments for their work during the upcoming Paris Olympics.
"Our demands are very reasonable and we will take whatever action we need to, to ensure our members receive what they rightfully deserve.”
Eurostar is expecting thousands of journeys for the Olympics and Paralympics but has reportedly recently cut fares due to a lack of demand. A further strike would be a major blow to the trainline and also fans travelling to the French capital to cheer on Team GB.
RMT has staged several strikes in the UK this year already but did u-turn on its plan for a Tube strike in April around a pay rise.
The RMT has told the Standard that it cannot comment further until the ballot on July 11.
An RMT spokesperson said: “Eurostar is very open to recognising the exceptional role key operational personnel will have during the Olympic and Paralympic Games. Discussions with RMT are ongoing and we continue to work closely and collaboratively with them.”