Migrants have tried to use Eurotunnel trains and the Channel Tunnel to cross to the UK / AFP/Getty Images

Part of the M20 is closed for queuing lorries, forcing traffic on to the A20, M2 and A2 as well as clogging local roads to the coast

Holidaymakers trying to use the Channel Tunnel are being warned of hours of delays today after “intense migrant activity” disrupted trains from France.

Eurotunnel services were temporarily suspended overnight and were struggling to get back on schedule on one of the busiest travelling days of the year.

The operator suspended services for a brief period shortly before midnight due to “migrant activity”, adding that French authorities were dealing with the situation.

Part of the M20 is still closed for queuing lorries trying to get to France

It tweeted: “Please be assured we always work hard to maintain the highest levels of security at our Calais terminal.

Travellers were warned of four-hour delays shortly before 7am this morning but trains are now running around 90 minutes behind, with a hour wait before check-in at Eurotunnel terminal in Folkestone.

Le Shuttle, which takes passengers across the channel in cars, buses or other vehicles, is running four services an hour and anyone arriving late will be put on the next train with space.

Eurostar, the high-speed train from London to Paris and Brussels for foot passengers, is unaffected by the disruption.

Miles of traffic jams continue on motorways into Kent caused by heavy traffic and diversions off the M20 on to the A20.

Operation Stack, which has shut the M20 between junctions eight and 11 for stationary lorries, is expected to remain in place until Sunday at the earliest.

The migrant crisis in Calais and intermittent strike action by French ferry workers means truckers are spending hours stuck in Kent and northern France.

Authorities at the Port of Dover are advising holidaymakers to use an alternative route on the M2 and A2 and allow plenty of time for their journey.

P&O ferries from Dover to Calais are also running with delays of up to an hour.

Passengers are being urged to check in as they would for their booked sailing and said that anyone arriving late will be put on the next available boat.

Philip Gomm of the RAC Foundation said: "Kent is a major gateway to and from Europe but once again that gate is well and truly shut.

“Operation Stack has become the rule rather than the exception, and on one of the busiest travel weekends of the year it is causing mayhem for hauliers, holidaymakers and local residents alike.”

Mr Gomm said that although the crisis that has seen thousands of migrants and refugees camped in Calais risking their lives to jump on lorries, trains or even swim to the UK is a job for international governments, more can be done to keep roads moving.

He added: “The depressing thing is that cross-channel disruption is nothing new and Operation Stack has been with us for almost 30 years. Yet only now are we seriously considering how to address its shortcomings.”