The people's plinth in Trafalgar Square

For 100 days, volunteers will stand - or cavort, sleep or perform - for an hour at a time on the vacant fourth plinth. The decision is set to create months of fun as Gormley presents "the widest range of human behaviour" with the project, called One And Other.

Unveiling his idea, the artist said: "The asylum-seeker, the person who is homeless, people who don't naturally think of this as being their kind of thing. We need the bodybuilder but we also need the paraplegic, the naturist, the Shakespearean actor..."

Mayor Boris Johnson was today announcing the decision made by the Fourth Plinth Commissioning Group, having come round to backing contemporary art in place of plans for a memorial to war hero Sir Keith Park.

The other choice from six submissions was Yinka Shonibare's Nelson's Ship In A Bottle. He will create a scale replica of HMS Victory, the battleship of Lord Nelson, the square's most famous resident, with sails made of textiles bought from Brixton market. It is not yet known which proposal will go up first - or when.

The scheme is funded by the Mayor, the Arts Council and private sponsors. Mr Johnson said: "I am very excited about the prospect of real people standing on the plinth in one of the great public squares of the world and I think it is an incredible idea to have a modern depiction of Nelson's ship that will be gazed upon by a statue of the great admiral himself."

Moira Sinclair, executive director of the Arts Council in London, said both proposals represented "the multiplicity of voices within our capital city".

Gormley had originally intended to have 8,760 volunteers for an entire year but the logistics were enormous. Stewards will need to be on site permanently and the plinth itself will be surrounded by a safety net.