Trafalgar Square's world famous fountains are going to be turned purple and magenta in a festive tribute to the London 2012 volunteers.

An audience of 3,500 volunteers, including Team London Ambassadors, London 2012 Games Makers, travel ambassadors and other Olympic volunteers, will be special guests at a carol concert at the central London landmark.

The ticketed event is hosted by London Mayor Boris Johnson.

He said: "Our fantastic volunteers were one of the great success stories of 2012 and proved to be the beating heart of the Games.

"It was truly remarkable how people from all walks of life came together to welcome the world to our great city.

"There is no better time to celebrate their contribution with a concert, than in this season of goodwill. I would like to thank all the volunteers and look forward to seeing many of them on London's streets in 2013."

Volunteering was one of the major successes of staging London 2012 by providing a welcoming face of the Games to millions of visitors to Britain.

In light of the successful use of the mayor's 8,000-strong team of volunteer ambassadors at the London 2012 Games, volunteers are to have a permanent presence in the capital.

They are set to be deployed at large scale events such as the New Year's Eve fireworks display, the Union of European Football Associations (UEFA) Champions League Final, Saracens Rugby Club home games, international rugby fixtures, the Sundance Film Festival, Barclays ATP World Tennis Tour Finals, Turkish Airlines Euro League Basketball Finals, Mr Johnson said.

Opera duo Jonathan and Charlotte are set to perform at the concert.