British workers on the Eurostar cross-Channel rail service will strike for seven days this month, including over a public holiday weekend, in a dispute over hours, a union said Wednesday.

Fifty-five members of the Rail, Maritime and Transport (RMT) union will begin the action this Friday, which the company said would see a maximum of four trains services cancelled each day of the strike.

Approved in a vote by RMT members, the walk-out will run from August 12 to August 15, and for three days over the weekend of August 27, which comprises a public holiday in Britain.

The RMT, which is currently staging a five-day strike on trains in southeast England over plans to downgrade the role of train conductors, said the Eurostar move was the result of a long-running dispute.

An agreement in 2008 over managing shift work and unsociable hours, to provide staff with a better work-life balance, had not been honoured, the union claimed.

"Our members are sick and tired of waiting for this," Assistant General Secretary Mick Lynch told BBC radio.

He said the walk-out would cause "fairly severe disruption" but added: "We don't want to be on strike, we don't want our members and the public inconvenienced this way. 

"We're ready to make an agreement today or tomorrow or whenever the company wants to speak to us."

A Eurostar spokeswoman told AFP the strike would result in the cancellation of a "maximum of two return trains a day, so four services". 

"We will of course be using more of our continental crew," she said, noting that the strike only affects British staff, and the company would bring in French and Belgian employees.

The company said it had been "working to find a joint resolution" with the RMT but refused to be drawn on any imminent talks.

"On the days of the strike we have made some small changes to our timetable to ensure that all passengers booked to travel will be able to on those days. Passengers affected will be notified in advance," a Eurostar statement said.