The death highlights the lengths migrants are going to in a bid to reach Britain amid the escalating migrant crisis in Calais

Britain's freight industry is losing £750,000 a day because of the huge problems lorry drivers have faced this summer trying to cross the Channel, freight transport chiefs have said.

The migrant crisis in Calais, wildcat strike action by ferry workers and protesting farmers mean truckers are spending hours stuck in queues in Kent and northern France.

Further delays hit cross-Channel services when the body of a suspected migrant was found on the roof of a Eurotunnel train at the Chunnel terminal in Folkestone yesterday.

And passenger and freight services were disrupted again today after reports of migrants invading the Eurotunnel terminal in Coquelles, in what has become a nightly occurrence.

An estimated 5,000 migrants displaced from countries including Syria, Libya and Eritrea are now believed to be camped in and around Calais.

Operation Stack - where freight traffic is queued on sections of the M20 when cross-Channel services are disrupted - remains in place, and Kent Police warned it could continue until at least Sunday.

But the Freight Transport Association (FTA) said the impact on Britain's economy was "horrendous" and that it was a national problem.

Its deputy chief executive James Hookham said: "Given the value of goods lost and the subsequent cost to business, these figures show that Operation Stack is not just an issue for Kent and the south east of England but a serious national strategic problem.

"This is the country's GDP and export standing still in these horrendous queues caused by the situation in Calais.

"It is simply not acceptable that industrial action in France can cause such chaos which is impacting on the British economy.

"Calais has to be made a strike-free zone so that cross-Channel traffic can start moving again and Operation Stack can be lifted as soon as possible."

More chaos is predicted this weekend, as the great summer getaway begins, because trucks are already stacked in miles of queues on the M20 and cross-Channel services report delays.

Kent County Council is hosting a multi-agency meeting in Maidstone where the FTA, Eurotunnel, Kent Police and other organisations discuss the crisis and try to come up with recommendations for the Government.

The mounting problems come as video footage emerged apparently showing migrants travelling to Britain on empty freight train carriages.

A number of people are seen in an otherwise empty carriage which arrived in Folkestone earlier this month, in footage from a worker obtained by The Sun.

John Keefe, from Eurotunnel, told the paper: "It is likely this group took advantage when the authorities were distracted by other migrants. Because of their activity in France we can't sometimes fully load a train."

The Port of Dover said the motorway was closed coastbound between junctions 8 and 11 following the problems at the Chunnel and high volumes of freight traffic.

But a port spokesman said it remained "open for business", with P&O Ferries and DFDS Seaways operating full services.

This month Home Secretary Theresa May announced that a new secure zone would be created at Calais for UK-bound lorries amid the escalating migrant crisis across the Channel.

The area will be able to hold more than 200 vehicles, taking them off the open road at the French port where they have been targeted by thousands of migrants trying to reach Britain illegally.

The Road Haulage Association (RHA) said the industry urgently needed a solution to the strikes that have been occurring in Calais, and to the threats posed to truckers and their loads.

RHA chief executive Richard Burnett said: "This is a crisis and demands swift and dramatic action.

"It appears that the tunnel is being laid siege to my many hundreds of people desperate to get to Britain.

"Tragically, migrants are being killed and our members are being subject to a daily gauntlet of intimidation and long expensive delays. It is also totally unacceptable that the people of Kent should bear this burden.

"I reiterate my call for the French government to put their military into Calais to secure the port and the tunnel terminal if the police are unable to do so on their own. By taking this decisive action, one of the main causes of Stack will be reduced."