Eurostar workers are to stage a 24-hour strike on August 28 in a dispute over pay packages, the RMT union has said.
Eurostar insists its services would not be disrupted
Customer service agents and platform staff at the cross-channel train operator voted two to one to reject a pay offer earlier this week.
The dispute is over wage differentials between workers in London and Kent, the RMT said.
Eurostar has said its services would not be affected by the strike and has described the action as "pointless".
RMT leader Bob Crow said Eurostar still had time to avert industrial action by returning to the negotiating table with a "fair and more equal" pay offer.
The union claims that workers earn "scandalously" low pay.
Starting salaries for some Ashford workers have remained at about £13,000 for the last decade, Mr
The RMT has claimed that workers at the terminal in Ashford, Kent, were paid around £4,000 ($7,293) a year less than staff at London's Waterloo station.
Eurostar, however, said the difference was £3,000 and a London Weighting allowance.
Eurostar said the strike action would involve around 160 customer services staff and would have no impact.
The company plans to run eight extra services from London to Paris and Brussels in response to passenger demand over the Bank Holiday weekend.
And staff would be redeployed from elsewhere in the company to cover for any striking workers.
The demands of the jobs at the main Eurostar terminal at London Waterloo and Ashford were different, Eurostar's public relations manager Lesley Retallack told BBC News Online.
"The RMT along with the other unions agreed a pay deal in the autumn of 2003," she added.
"The dispute is about improvements to our staffing and salary structures within the customer service team."
Eurostar said it pays customer service staff around 50% more than its airline competitors and has a 98% retention rate.