The BBC's Robin Gibson: "Some of the worst hold-ups ever seen in the UK"

All ferry services on the busy Dover to Calais route have been suspended as a Sea France staffing dispute on Wednesday afternoon snowballed into a lock-out by French dockers.

Police at the southern English port have taken emergency measures - codenamed Operation Stack - to cope with the influx of more than 120 heavy lorries every hour.

Operation Stack can park 3,500 lorries

Junctions 11 and 12 of the M20 in Kent have been closed to allow lorries to be parked. Junctions 8 and 9 are also likely to be closed during Wednesday evening to create space for up to 3,500 vehicles.

Dover town centre became completely gridlocked and was only cleared after several hours as police began to divert light traffic away from the area.

The misery was further compounded during the afternoon as a false fire alarm in the Channel Tunnel resulted in the suspension of services while a train was evacuated.

The tunnel later reopened.

Ferry companies are taking legal action

The dispute began over the appointment of a purser - an officer who keeps the accounts - on a Sea France ship. This prompted crews to take unofficial action, which the company branded "illegal".

The crews then persuaded Calais dockers to support their strike and all vessels were turned away.

Massive queues formed on both sides of the Channel as P&O Stena became the first operator to re-route its service via Zeebrugge in Belgium.

A spokesman said: "Once again we're caught in the middle of a dispute not of our making and it is deeply frustrating for us and our passengers."

P&O Stena and Sea France are seeking injunctions through the French courts to prevent any further industrial action.

Kent Police have issued warnings of long delays and diversions.