Long queues greeted the launch of the latest artwork to take up residence in Trafalgar Square - seven transport containers illustrating the suffering of women trafficked as sex slaves.

The installation was championed by actress Emma Thompson, along with human rights campaigner Helen Bamber and Sam Roddick, daughter of the late Body Shop founder Anita.

The crates are the kind used to smuggle people into Britain, but have been painted with images designed to shock the viewer into awareness of the realities of the sex trade.

Together they form an installation, Journey, which represents the experiences of sex slaves as they are brought into this country.

Members of the public yesterday wandered inside the seven crates - individually titled Hope, The Journey, The Uniform, The Bedroom, The Customer, The Stigma and Resurrection - moving from a simple bedroom in a family home to the horror of a locked room in London, where the newly broken prostitute might be expected to service 40 clients a day.

Visitors to the exhibit were invited to sign a petition asking the Government to ratify the European Convention Against Trafficking.

Oscar-winner Thompson, who heads the trustees of the Helen Bamber Foundation Trust, said: "Londoners are not aware of sex trafficking, but it's right on their doorstep.

"Last year I met a woman whose life had been taken away through trafficking. She had been around the corner from my house in a massage parlour." Thompson added: "I felt that because it is the 200th anniversary of the abolition of the slave trade, we had an opportunity to highlight the slave trade still going on."

Ken Livingstone, the Mayor of London, agreed to mount the show in Trafalgar Square after Thompson used her high profile to secure an interview with him.

The installation will move to Glasgow and Liverpool later this year, after which Thompson hopes to take it to the Eastern European countries where many victims originate.

Four thousand women are working as prostitutes after being smuggled into the UK, according to a recent report by the joint Lords and Commons Human Rights Committee.

It said that a decade ago 85 per cent of women working in brothels were UK citizens, but today 85 per cent come from overseas. England is now thought to be Europe's sex-slavery capital, with three quarters of London's prostitutes coming from abroad.

The Journey containers will be open every day until Sunday between noon and 8pm.