Like many migrants drawn to the French port of Calais, Ali, a 22-year-old Iraqi, is convinced his life will be better if he can make it across the 30 km (20 mile) stretch of sea separating him from Britain.

"I know people in London, they can help me and it will be a new life," Ali said, speaking on the outskirts of a Calais migrant slum. "It cannot be worse than in France."

Dislocated by war, political turmoil and poverty, 3,000 migrants like Ali are living in makeshift camps in and around Calais, hoping to find a way to the other side.

If they make it, they expect to find illicit employment in Britain's booming shadow economy or to claim asylum in a system often seen as more generous than the French equivalent.

Such beliefs are encouraged by the networks of traffickers who squeeze money out of migrants at every stage of their journey from the war zones of the Middle East and from Africa.

But for the few who make the crossing, that expectation may be wide of the mark.

"All the belief that the roads of London, the roads of Britain are paved with gold – this is not the situation," said Habib Rahman, Chief Executive of the Joint Council for the Welfare of Immigrants, a British organisation.

"What we know of the people here is that they are really struggling."

Calais, which has sea and rail links to Britain, has been a migration bottleneck for centuries, but tension has risen in recent weeks due to a French ferry workers' strike which has blocked traffic around the port.

Television images of migrants lining roads and scrambling to jump into moving vehicles have provoked public and political anger, providing a stark illustration of a growing Europe-wide immigration crisis.

British Prime Minister David Cameron said the scenes were "totally unacceptable" and ministers from both France and Britain have pledged to increase security around the port to protect the economically important flows of goods and tourists across the channel.

Britain has sent a two mile long 9 foot (2.75 m) high fence, last used to secure the 2012 London Olympics, to help keep migrants away from the entrance to the rail tunnel linking the countries.

"Why England?"

For many of those in Calais, the risks, which include suffocation in the backs of trucks, falling from moving vehicles and violence in migrant camps, are worth taking for a chance of entering the British system.

"I ended up here when I left my country where I risked my life. I fled. I do not know where to go, but not here," said 25 year-old Aman, an Eritrean interviewed by Reuters near Calais. "Why in England? I was told that it was better."

Britain's economy overtook France to become the second largest in the European Union last year, according the International Monetary Fund, and Britain is forecast to grow twice as fast as France this year.

With support groups denouncing the living conditions of migrants in Calais as inhuman, the French government has opened a reception centre just outside Calais with showers, toilets, washing facilities and electricity.

But the outspoken mayor of Calais, Natacha Bouchart, said earlier this year that Britain offered the most generous conditions for migrants in Europe.

Christian Salomé, president of L'Auberge des Migrants, a French group that helps migrants, said the reasons were more deep-seated than access to government money.

"In England, when they file an application for asylum, they have shelter, they exist, they are recognised," he said. "In France, they submit an application and they go back to a slum."

Salomé said many eschewed France and other European countries they had travelled through for a life in Britain because they could speak English, or had family members already living there.

However, the thrust of political efforts to deter migrants has focused on tightening security and reducing the financial 'pull factors'.

Britain and France on Thursday pledged "joint information campaigns to inform migrants of the reality of Great Britain's asylum and benefits systems".

POVERTY LINE

In France, asylum-seekers receive basic and emergency medical care and their children must attend school. Asylum-seekers not in a state centre receive 11.35 euros (£8) per day, while those in shelters receive from 91 euros (£64) to 718 euros (£518) a month depending on criteria such as the size of their family.

In Britain, asylum seekers are not entitled to work or claim payments from the mainstream welfare system but are able to use public services such as the National Health Service.

A single adult is entitled to a special asylum seeker payment of £36.95 per week and for those who arrive without money or accommodation, the state provides housing.

"As they are barred from working, asylum seekers are forced to live in poverty and they have no choice but to rely on the government to provide them with somewhere safe to sleep at night," said Dr Lisa Doyle, Head of Advocacy at the London-based Refugee Council.

British statistics show more than 9,000 people were granted asylum in the year to March 2015, while more than 25,000 applications were received. If given asylum status, they have the same access to benefits as a British citizen.

Those who choose to work illegally rather than claim asylum are not entitled to any welfare cash, and immigration laws due to be passed in the next year will introduce powers to confiscate their wages, if caught.

"Since 2010 we have made it systematically harder for people to illegally enter, work and remain in the UK," Cameron's spokeswoman said.

She said the new offence of 'illegal working' would make it clear to migrants who have no right to be in Britain that working illegally in the UK is a crime, with consequences for their earnings.

But for Ali, interviewed outside the recently opened but already oversubscribed Jules Ferry migrant day centre in Calais, nothing the British government is doing has deterred him, or stopped his friends advising him to make the crossing.

"We phone each other, they are not treated as we are here in France, where we are like animals. I just want to be a human being," said Ali, who was unemployed and without professional qualifications in his native Iraq. "Some have managed to pass the frontier, so I am also trying."