Passengers are being helped to make other arrangements

P&O has laid off two ships and is operating four, the company said.

"We are shuttling ferries back and forth and trying to keep delays to a minimum. If you have to travel, expect big delays," spokesman Brian Rees said. SeaFrance said 10 of its 15 crossings would be unaffected and SpeedFerries said its Dover-Boulogne service was sailing according to schedule.

P&O has asked passengers to contact the firm to make arrangements to travel at other times.

The berth now under repair at Calais was damaged when a loading bay collapsed at the port last month, leaving the port with only two berths big enough for large cross-Channel ferries.

Last week, P&O warned that its services from Dover would be subject to more delays and cancellations for three days.

Ferries were also disrupted by a 24-hour national strike in France last week.