Rail workers at Eurostar said on Wednesday that they are planning a seven-day strike during August.
The dispute is over their work-life balance which members say is being undermined repeatedly.
Members of the Rail, Maritime and Transport (RMT) union will stop work over two weekends – Friday 12 August to Monday 15 August and then again over the British bank holiday weekend from August 27th.
The union accused Eurostar of failing to honour a 2008 agreement which provided for train managers to expect to balance out unsocial hours on duty.
Eurostar has suggested that it did not expect the strike to have great impact on services, despite some 80 train managers being involved.
It plans some “small changes to our timetable” so that passengers will be able to travel on those days.
The RMT general secretary Mick Cash said: “Our members have every right to have a fair work-life balance that fulfils operational needs of the company while guaranteeing quality time off for friends and family.
“It’s now time for Eurostar to come to the negotiating table with a set of proposals that honours our agreements and guarantees our members a genuine work-life balance.”