British Prime Minister David Cameron has been criticised by the charity Refugee Council for "dehumanising" remarks he made on the ongoing migrant crisis in Calais.

In a television interview Cameron had blamed the situation on a "swarm" of migrants crossing the Mediterranean.

Anna Musgrave, Advocacy Manager at Refugee Council, said the PM's choice of language was "irresponsible" and that he had misunderstood the numbers estimated to be attempting to cross the channel through the Eurotunnel.

"I think it's extremely disappointing to hear the Prime Minister using such irresponsible and ultimately dehumanising language," said Musgrave.

"But I'd actually go further than that. I'd suggest that the Prime Minister is in fact misinformed. He was talking about the 200,000 people that we've seen making that treacherous journey across the Mediterranean. He suggested they were all en route to the UK via Calais.

"This is quite patently false. Estimates suggest we're talking about 3,000 in Calais, a tiny number of those that have made that journey and dwarfed by the numbers that Greece and Italy are receiving.

"I would say it's incumbent on the Prime Minister to show leadership, to use responsible language, to remember we're a country with a proud tradition of protecting refugees and upholding human rights.

"Bearing in mind that it's understandable that people feel alarmed by some of the images that are coming through on their TV screens and that's why it's so important that the Prime Minister shows leadership on this and doesn't fuel fears," she added.

Musgrave explained that the world is in the midst of a major refugee crisis, and that it is the poorest countries who are hardest hit.

"What we're seeing is a symptom of the fact that the world is in the grips of the worst refugee crisis since the Second World War," Musgrave said.

"The vast majority of those refugees are actually hosted by some of the world's poorest countries. A small proportion are risking their lives crossing the Mediterranean in search of safety in Europe, and a tiny tiny proportion are trying to reach the UK. We must remember that the UK hosts only about 1 percent of the world's refugees."

She went on to call for EU countries to look at their immigration policies, which she blamed for forcing migrants to take often life-threatening measures in order to reach safety in Europe.

"It's important that all EU countries make sure that people have access to a fair asylum system. But I would say actually we need to look at the root causes of the problem actually, and we need EU countries to work together, both to address the root causes of why people are being forced to flee in the first place, but also to look at our immigration policies," Musgrave said.

"Why are they getting on that boat in Libya? Why are they forced to try and clamber aboard Eurostar? It is because of our immigration policies that make it impossible for refugees to find safety through legal and safe means."

Meanwhile, freight and passenger traffic through the rail tunnel remained severely disrupted on the British side on Thursday.