Eurotunnel says the problem of illegal immigrants using the Channel Tunnel to enter the UK is hitting its performance.
The tunnel operator said stowaways are making "nightly intrusions" into its freight terminal at Coquelles, near Calais.
Chief executive Mr Philippe Lazare says the business, which has reported a 4 per cent dip in revenues, has also been hit by the economic slowdown and foot-and-mouth disease.
Eurotunnel says it is devoting "considerable effort and resources" in its bid to stop illegal immigrants and said help from the UK and French governments is 'indispensable'.
The Home Office has threatened to charge Eurotunnel £2,000 sterling for each illegal immigrant it unwittingly brings into Britain after discovering that about 1,000 stowaways are using the route each month.
In its interim results, Eurotunnel says its freight shuttle service saw a 9 per cent increase in traffic, but its car shuttle service saw a 9 per cent fall in passenger numbers.
The company said it made a net loss of £61 million in the six months to June 30th, compared with a net loss of £78 million in the same period last year
It said its first-half sales were £265 million, compared with recalculated sales of £276 million last year.
PA