Truckers are being left as "sitting ducks" to migrants attacks because of industrial action by French customs officials, campaigners claim.

Lorry drivers trying to sail back to Dover have been held up in queues for as long as 12 hours during the work-to-rule action, where staff work their exact work hours of their contract to reduce output.

The dispute, which is continuing beyond March 29, is aggravating an ongoing problem, which has included cases of at least one woman driver being threatened with rape if she did not let illegal immigrants on board her vehicle.

Now Britain's Road Haulage Association is calling for French soldiers to protect lorry drivers who have been threatened, even with guns.

It says the industrial action has worsened a problem suffered by truckers at the hands of migrants and traffickers, particularly over the last four years.

The problem is also being fuelled by the belief among migrants that it may be harder to get into Britain after March 29, the scheduled date for the UK to officially leave the EU, although this is widely expected to be delayed.

An RHA spokesman said: "We had feedback from one lorry driver saying that he was kept waiting for 12 hours two weeks ago trying to board a ferry from Dunkirk to Dover.

"First for us comes the welfare of drivers and they are sitting ducks to migrants. They have been threatened with baseball bats, chains, knives and guns."

Migrants tried to break into that lorry held up outside Dunkirk.

A colleague added: "We had a report from a woman driver who was told if she didn't let migrants into her cab she would be raped.

"That particular incident happened 18 months to two years ago outside Calais but it shows these migrants will stop at nothing to get into the UK. We have already said that the French military need to be brought in."

There has been a long history of migrants in northern France trying to break into lorries bound for Britain via Dover.

But, the RHA say, the problem has been worsened over the last four years with an increase in migrant movement through Europe, particularly from Syria.

RHA members have reported chaos at both French Channel ports and Eurotunnel as customs officials have since March 4 been taking action.

Already by the next day there were several miles of lorries backed up long the A16 motorway leading to Calais and the Channel Tunnel entrance.

It is in a dispute over working conditions and fears of a no-deal Brexit and the action is expected to continue until April 1.

One haulier told the RHA that they had abandoned a number of planned Channel crossings last week .

RHA chief executive Richard Burnett says drivers have a right to do their job safely and shouldn’t be left vulnerable to attacks from migrants and people smugglers.

“Yet again we’re hearing horrifying stories of truckers running a gauntlet of people trying to break into their lorries. It’s completely unacceptable. The French authorities need to do more to protect UK-bound lorries."

French customs officials demanding more pay and staff to deal with the expected extra work from the impact of Brexit.

They want higher pay and say their action is showing what will happen if greater controls are put in place once Britain leaves the European Union,

The French trade unions federation UNSA (Union National des Sydicats Autonomes) says that agents are doing longer checks than usual, so immediately causing traffic jams.

The Road Haulage Association has also complained about a lack of clarity over border crossing processes after Brexit.

The disarray continued in Parliament last Tuesday when Premier Theresa May was again heavily defeated over her Brexit deal.

Another vote is expected on it this week but MPs have also voted to put back the leaving date from March 29.

Mr Burnett, speaking even before last Tuesday's vote in the Commons, said: “It is patently clear that government has lost its way. There are some momentous decisions to be made both in the run up to Brexit and beyond. Yet tens of thousands of UK hauliers responsible for keeping the supply chain between the UK and the rest of Europe are still in the dark. Because of government ineptitude they are simply not ready.”

The RHA stresses this is also about the economy and the millions of UK and European businesses relying on an effective supply chain.

It says that those whose livelihoods depend on a smooth and dependable distribution network will suffer, for example those carrying and those waiting for perishable goods and medicines.

Almost exactly a year ago, last March 15, Transport Secretary Chris Grayling had insisted that a free-flowing border at Dover would remain.

He said: "We will not impose checks in the port.

" We don't check lorries now - we're not going to be checking lorries in Dover in the future. The only reason we would have queues at the border is if we put in place restrictions that created those queues - we are not going to do that."

But Mr Burnett now said: “This is at odds with the reality of the situation.

“It’s misleading. If the French are going to check both inbound and outbound trucks the timing of the supply chain into the UK will be severely affected.

“The whole situation has turned into a farce as is being clearly demonstrated in Calais right now. And, through no fault of its own the industry on which the economies on both sides of the Channel rely so heavily is being set up for a fall of catastrophic proportions."

Mr Grayling had by chance been speaking on a night the debate programme Question Time was recorded at the Dover Cruise Terminal and transmitted.