Six artists have been shortlisted to produce the next commission for the vacant Fourth Plinth in Trafalgar Square, which is currently occupied by Yinka Shonibare's Nelson's Ship in a Bottle.

An exhibition is due to start in the crypt of St Martins in the Fields on 19 August to showcase preliminary models and sketches from each of the artists' proposals for the scheme. Allora and Calzadilla; Elmgreen and Dragset; Katharina Fritsch; Mariele Neudecker; Hew Locke and Brian Griffiths are vying for the commission, which will replace the plinth's current occupant at the end of 2011.

The Fourth Plinth Programme is a rolling initiative to install new artworks in Trafalgar Square, with funding provided by the mayor of London and Arts Council England (ACE). London mayor Boris Johnson said: "'It's that time again, when the art world braces itself for a spurt of bold ideas for what is surely the premier public art spot in Britain.

"This is the chance for today's most exciting artists to create something in one of the most historic and traditional settings imaginable. We can only guess what they will come up with - but I have no doubt it will get everyone talking." Image: The current occupant of the Fourth Plinth – James O Jenkins