People travelling back to the UK are being warned of delays next week because of a strike by Border Force staff.
As part of a long-running dispute over pay, jobs and pensions, members of the Public and Commercial Services union in Dover, and French ports including Calais and Dunkirk, will take industrial action between February 17 and 20.
Officials said they had made extensive plans to minimise disruption, including training military personnel, civil servants and volunteers to step in.
The government said the strike focused on inbound travel to the UK from Calais, Dunkirk and the Coquelles Channel Tunnel Terminal.
It said it would also affect the Port of Dover, and that all those who are due to travel into any UK port during the strike should be prepared for longer waits.
“It is disappointing for travellers that yet again strike action may cause disruption for those entering the UK," said Steve Dann, Border Force chief operating officer.
“Border Force’s number one priority to is keep our citizens safe and borders secure.
"We are working together with partners across the travel industry and our French counterparts to ensure we can continue to meet critical demand and support the flow of passengers and goods through our border.
“During the periods of industrial action, travellers should be prepared for disruption. We encourage everyone to check the latest advice from your operators before travelling.”
The union has urged those affected by the strike to direct their frustration at the government.
