French ferry workers have walked out on strike in Calais, leading to the port's closure and chaotic scenes on roads leading to Dover.
It is the second time in a week that MyFerryLink workers in France have taken industrial action the company's ferries were sold to rival DFDS Seaways. On 24 June, during the last strike, there were violent scenes as thousands of migrants tried to board lorries bound for Britain that were stuck in Calais.
All ferry services between the Port of Dover and Calais are affected by the action, although DFDS is still sailing to Dunkirk as normal.
Transport Secretary Patrick McLoughlin chaired an emergency Cobra meeting, and said: "We're looking at the situation and working with the French government."
A Port of Dover spokesman said: 'We will continue to monitor the situation closely in liaison with our ferry partners and the Port of Calais in order to resume normal operations as soon as possible. Please note that there may be delays to services when the Port of Calais re-opens.'
Customers were advised to contact their ferry operator before travelling.
Highways England said Operation Stack, where lorries use part of the M20 to Dover and Folkstone to queue for Channel ferry crossings, has been implemented.
A Eurotunnel spokesman said: "At the moment the strike is affecting the port and ferry services only and all our services are running well. We are braced with contingency plans should that change."