The Conservatives, Labour, Lib Dems and UKIP are all proposing tighter border controls, with a recent poll suggesting immigration was the third most important election issue behind only the NHS and the economy.

It has proven a catalyst for a wider debate about Britain's place within the European Union, with UKIP arguing that free movement of workers and a rising migrant population is putting too much pressure on public services and driving down wages by undercutting British workers.

Against this background the Joint Council for the Welfare of Immigrants (JCWI) - which campaigns against discrimination - is spending £44,000 on a UK-wide poster campaign, with the aim of "humanising the debate".

BBC News met four people who are some of the charity's faces of the "I am an immigrant" campaign:

"Without immigrants the NHS would collapse," says 40-year-old S Chelvan, who arrived in the UK from Sri Lanka aged four.

His parents moved him to the UK to escape riots in his home country, and his mother worked in the NHS.

He says: "The seismic shift recently has been to concentrate on EU migrants. That didn't really used to be part of the debate 10 years ago. The reason for this is that various political parties felt they were losing the debate on Europe on other issues, so migration is the easiest way of opening the anti-Europe debate."

Mr Chelvan says many of those who are against immigration "fear difference" and often blame migrants for "failings in their own lives", adding: "So now we have the dehumanisation and stigmatisation of the migrant."

"As a musician I have always moved around," says violinist Nicolette Moonen, who moved to the UK from Holland in 1992 and teaches at the Royal Academy of Music in London.

In 1996 Nicolette founded The Bach Players and the group holds a regular concert series in London and has performed all over the UK.

"Wherever I go my common language is music," says the 59-year-old.

And she believes immigration is an issue that the whole nation needs to address.

"The dog barks at the stranger, but when the dog knows the person it wags its tail. We want to this to happen with society's view of migrants," she says.

Mary Sithole says in the last five years she has noticed the debate around immigration become more vitriolic.

"It has made me wonder if I'm really in the right country," says the 40-year-old, who escaped from Zimbabwe in southern Africa when she was just 20 because her family feared for their lives.

She adds: "If people are saying things about the Polish and Romanians then it only makes me think, 'what are they saying about me?'"

Lois Lau, 32, moved from Malaysia to the UK, aged 13, because her mother worked for the NHS.

On 29 April she will be representing England in the international touch rugby finals in Australia. She was also part of the England team that won gold in the non-contact sport at the European championships last year.

"For me people's attitudes on immigration have not got any better than when I first arrived in the country," she says.

Saira Grant, far right, says it is "ridiculous" for parties to try to cap net migration to the UK

Saira Grant, legal and policy director for Joint Council for the Welfare of Immigrants (JCWI) says that the tone of public discussion about immigration is "contributing to a climate of hostility and fear".

Her campaign is not party political, she says, but argues it is "absolutely ridiculous" for parties to put a specific cap on net migration. The Conservatives were criticised for missing a target to reduce immigration to "tens of thousands" by May, as it rose to 298,000.

Labour has said it got it wrong on immigration when last in government, failing to take into account the impact on public services and driving down wages.

Meanwhile, UKIP leader Nigel Farage has said he would like to see the number of immigrants to the UK "below 50,000 a year" but says an overall cap on net migration would be "ludicrous".

From Monday 13 April, posters will go up at 400 London Tube stations, with larger posters appearing on billboards at railway stations across UK.

Source: The BBC