THE Prime Minister has said that chaos in Calais will last all summer, as representatives of Scottish haulers claimed one driver caught up in the turmoil had been threatened with a gun.

David Cameron yesterday described the situation at the French port as "unacceptable" after thousands of migrants attempted to reach the UK in recent days. Chronic tailbacks have built up on the M20 as lorries face lengthy delays to access the Channel Tunnel.

The Prime Minister said that extra sniffer dogs and fencing were being offered to authorities in Calais, although critics branded the move a "sticking plaster". Mr Cameron admitted: "This is going to be a difficult issue right across the summer."

Martin Reid, director of the Road Haulage Association for Scotland and Northern Ireland, warned that the situation was having a huge impact on Scottish business. His organisation has launched a petition calling for the French Government to deploy its military to restore law and order.

He said: "The drivers are getting threatened by migrants and are getting very limited help from the police over there. They feel they are on their own. They are being threatened with weapons, and in one case we know of someone was threatened with a gun. They're just trying to do their job and it's not acceptable.

"The guys are not keen to leave their cabs in Calais, it's opening them up to migrants trying to get on their trucks. Chaotic is the right word. We don't feel the police over there are doing enough or can handle the situation."

In terms of Scottish business, Mr Reid said that seafood suppliers were being particularly hard hit, as delays meant produce was spoiled before it could be delivered.

DR Collin, based in Eyemouth, exports seafood including mackerel, squid and lobster to many companies in France, by sending two lorries across the Channel every day. The crisis has cost the business £100,000.

"Part of what Scotland does very well is export seafood and shellfish," Mr Reid added. "That sector has been hit very, very hard. These are high value items being spoiled and the knock-on effect is massive. There's no point going out fishing if you can't deliver.

"There's been no sign of anything improving. Cameron's talking about fencing and sniffer dogs, but that's just a sticking plaster when we've got a major problem that needs to be sorted."

The Freight Transport Association (FTA) echoed concerns about the impact on Scottish business, saying some drivers were being delayed for up to 20 hours in Kent before being allowed to cross the channel.

Margaret Simpson, the FTA’s Scotland manager, said: "The situation in Calais is having a huge impact on the Scottish freight industry. The delays on both sides of the Channel are causing financial and logistical implications for operators and it can’t be allowed to continue. Every year we are subject to disruptions of some kind at the French ports and the migrant issue this year has simply compounded an ongoing problem."

The Prime Minister, returning from his visit to south east Asia, chaired a meeting of the Cobra emergency committee yesterday to discuss potential solutions. It came after a fourth night of disruption at the terminal in northern France, while migrants' desperation to reach Britain was laid bare in an extraordinary picture showing two clinging to the top of a lorry as it arrived at Folkestone in the early hours of yesterday morning. There was more disruption in Calais yesterday, where an estimated 5,000 migrants are present, as striking ferry workers burned tyres causing gridlock.

Britain will work "hand in glove" with the French to tackle the problem, Mr Cameron said. "The situation is not acceptable and it is absolutely this Government's priority to deal with it in every way we can," he added.

"We have got people trying to illegally enter our country and here in Britain we have got lorry drivers and holidaymakers facing potential delays. We are absolutely on it. We know it needs more work."

A spokeswoman for the Prime Minister said "urgent options" are being pursued by defence and transport planners to create alternative parking zones to alleviate the pressure in Kent. This may include a temporary freight overspill at Ebbsfleet, while increasing ferry capacity on different routes is also being explored.