Thirteen feet high and carved from a single piece of white marble, the statue of pregnant, disabled woman becomes the latest work of art to stand on Trafalgar Square's empty plinth today.

Alison Lapper Pregnant, which is modelled on a disabled artist from Brighton who posed for Marc Quinn, the sculptor, when she was eight months pregnant, will be unveiled by Ken Livingstone, the Mayor of London, this afternoon.

Ms Lapper, who was born with shortened legs and no arms because of a congenital disorder, has travelled to London for the ceremony. "I’m very excited about it. This is history in the making," she said.

"Never before has someone with a disability - let alone someone with a disability who is naked and eight months pregnant - been put in such a public place and portrayed in such a positive way."

Ms Lapper acknowledged the strong, positive reactions that the statue has drawn. Greg Hilty, director of visual arts and literature at Arts Council England, London has celebrated the work for its consideration of "idealism, heroism, femininity, prejudice and identity."

While Bert Massie, Chairman of the Disability Rights Commission, said: "I’m extremely proud that one of the most popular tourist attractions in London is displaying a very powerful sculpture of a disabled woman."

Mr Quinn expects the piece to surprise passers-by in London's most famous square: "Hopefully that first shock will draw your attention to the sculpture and then, once it’s got under your skin, there will be an emotional response to it," he said.

This morning, critics of the work voiced their dislike for it in careful terms. Robert Simon, editor of the British Art Journal, told BBC News that the statue was "horrible".

"Not because of the subject matter I hasten to add," he said, praising Ms Lapper for her role in the project. "I think she is very brave, very wonderful but it is just a rather repellent artefact - very shiny, slimy surface, machine-made, much too big."

The sculpture, which is made of 13 tonnes of white Carrera marble, will remain on the plinth for 18 months before being replaced by Thomas Schutte’s perspex installation "Hotel for the Birds" in 2007.

Trafalgar Square's fourth plinth was built in 1841 by Sir Charles Barry and was intended to display an equestrian statue.

But a lack of money and agreement over what should stand on it left the plinth empty until July 1999, when Mark Wallinger's Ecce Homo: Behold the Man, a life-size statue of Jesus Christ, became the first of a series of temporary installations in the square.

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