SeaFrance crossings from Dover to Calais have been suspended for a third day as a strike by ferry officers in France over a pay dispute continues.
SeaFrance said talks were under way with staff
P&O Ferries between the Kent port and Calais are also severely delayed, along with the Norfolk Line from Dover to Dunkirk, due to high winds.
It has led to traffic backlogs in Kent and the M20 has been closed coastbound to allow lorries to park.
Phase two of Operation Stack is now in place between junctions eight and 12.
Non-freight traffic is being diverted on to the A20, causing traffic delays and Kent Police advised drivers to avoid the area where possible.
A spokeswoman said Operation Stack was expected to be in place for the rest of the weekend, with storm force winds possibly closing the Port of Dover.
SeaFrance and P&O both advised customers to check with the ferry companies before travelling.
A spokeswoman for SeaFrance said it was booking all passengers on to alternative crossings with other operators.
"SeaFrance is working to end the action as soon as possible and contact between the parties is ongoing," she said.
"However the union demands amount to the equivalent of an 25% increase in salary costs over three years, which the company considers excessive and is not in a position to consider."
Eurotunnel advised travellers to allow extra time for journeys to the terminal because of the closure of the M20.
It said it was experiencing extra traffic because of the ferry disruption and travellers were waiting up to 90 minutes at check-in and 90 minutes in the terminal.
In north Kent, the A249 Sheppey Crossing bridge was also closed because of strong winds, with traffic being diverted via the Kingsferry Bridge.