Eurostar rail workers from two unions are to take part in two periods of strike action this month in a dispute over their work-life balance.
RMT members will walk out from Friday to Monday and from August 27 to 29 while TSSA members will strike on Sunday and Monday and on August 28 and 29.
Transport Secretary Chris Grayling said he was “very disappointed the unions keep calling strike action over what appear to be pretty minor matters”.
Eurostar said all passengers with reservations would be able to travel.
The firm runs services between London and mainland Europe.
A company spokesman said: “On the days of the strike we have made some small modifications to our timetable to ensure that all passengers booked to travel will be able to travel on those days.
“Customers affected by any changes will be notified in advance with options for their journey.”