Lack of food and shelter fuels ever more desperate attempts to reach UK and sparks call for Cameron to act

The mayor of Calais threatened to use the town's population as a human barricade to blockade its port on Thursday night, as paramilitary police were drafted from around France in a bid to prevent increasingly desperate attempts from a growing number of migrants attempting to get to the UK.

As dusk fell on a patch of scrubland a five-minute walk from the stately town hall of Calais, hundreds of migrants gathered at a soup kitchen, and said that despite the heavy police presence they would continue in their attempts to get across the Channel.

"Sometimes I try one time in the day, sometimes three, but I try every day," said Saqi Raja, a 24-year-old from Pakistan, who had been in Calais for two months. "It is very bad here. The police have beaten me up – but I keep on trying."

As the meals ran out, a snaking line of migrants – mainly men, but also including several young boys – began to make their way back towards the centre of town and the port.

Politicians and local charities warned on Thursday that the number of migrants attempting to reach the UK was growing every day, and said there was a new desperation among them.

That was evident on Wednesday when a group of close to 100 migrants pushed through security barriers at the port and attempted to storm a tourist ferry bound for Dover. A further group of at least 150 migrants attempted a similar feat hours later, but were stopped by police.

A makeshift encampment of migrants near the Calais ferry port. Photograph: Oli Scarff/Getty Images

At a tense press conference at the town hall on Thursday the mayor of Calais, Natacha Bouchart, threatened to call on the people of the town to become a human barricade, and block the port until further action was taken by the British government.

"My proposal [to block the port] still remains. We are sick of not being listened to," she said. "There needs to be a realisation that the people of Calais have suffered in this situation for 12 years. Until now we have had no help, no word of compassion and no support … It is time for the UK government to take responsibility."

She acknowledged that blockading the port would be illegal, but said: "Do you think it is legal and fair to leave us in this situation?"

Asked what immediate action she wanted from the British government, she said: "We want the British government to send a message that migrants from Calais will not be welcomed."

She also demanded financial compensation from Westminster, called for the UK border to be placed in Britain rather than Calais and called for David Cameron to visit the town.

On Thursday night François Guennoc, from the charity Immigrant's Inn (Auberge des Migrants) was attempting to meet the needs of the hundreds of migrants queuing for food. "More and more migrants are coming and sometimes we don't have enough food to give them. We are having to reduce the portions and really sometimes it is not enough to feed one person," he said. "The situation is very difficult here. There are not enough places to shelter. People do not feel safe – they feel afraid."

A 20-year-old Sudanese man, who did not want to give his name, explained he had been in the town for just a few days after crossing Europe over several months, and said existing was a struggle. "Conditions are very bad. We are hungry. We are dirty," he said. "What can we do? How can we survive?" Asked why he wanted to get to Britain he said: "Here you cannot get papers, you cannot work – they do not want us here."

The number of migrants in Calais has increased sharply in the past few months, after dwindling in recent years, with an estimated 1,000-1,400 migrants in the town and immediate region, according to the UN High Commissioner for Refugees.

Over the summer tourists returning from summer holidays have seen migrants attempting to break into lorries, caravans and in some cases cars in desperate attempts to make it to the UK.

A British woman told of her shock at finding a stowaway hidden in her Fiat Panda after she had travelled from France to the UK.

"While we have seen similar or even higher levels of migrants before, what seems to be getting worse is the desperation, with people willing to take ever greater risks," said William Spindler of the UNHCR. The agency said that when the informal camp known as the jungle was cleared in 2009 many of the migrants were fleeing Afghanistan, and had travelled through Turkey and Greece.

Today's migrants are, in the main, from Somalia, Sudan and Eritrea, and have travelled from north Africa to mainland Europe, often through Italy, while others are fleeing the conflict in Syria.

Violent clashes between rival migrant groups and people smugglers have also broken out in the town as French police operate zero-tolerance tactics that see migrants constantly moved on.

"The police will not let them concentrate in any place. They are constantly being harassed, which is putting them under more pressure," said Spindler. Any makeshift camp set up by the migrants is destroyed, leaving them to seek temporary shelter in squats around the town. "There is no water, no toilets. They are infested with rats," he said. "They tend to keep a low profile or they are dispersed."

Local pensioner Lilian Rombert, said she felt desperately sorry for migrants who found themselves in limbo in Calais. "I think it is very sad, they are dirty and hungry – we have to do something to help them," she said. "Since the summer there have been a lot more, we need to find some kind of solution."

The UNHCR closed its office in July 2012 after migrant numbers dropped in Calais. But it is now working with the local authorities in Calais, which is planning to open a day centre for migrants to provide support and advice – although no shelter – to migrants away from the influence of people smugglers.