COI has been appointed to handle the search and three agencies have been shortlisted to pitch for the business.
London & Partners will be the official promotional agency for London from 1 April, responsible for promoting the capital as a leisure tourism, business tourism and major event destination.
The organisation has been formed by Boris Johnson as a way of bringing together a number of existing agencies that already work on publicising London. Among the companies that will be consolidated under the umbrella agency are Visit London, Think London and Study London.
Johnson hopes that the new agency will provide a more "co-ordinated and strategic approach to international promotion" in the run-up to and during the 2012 Olympics.
The successful agency will be responsible for handling campaigns for London & Partners to help increase the number of tourists that choose to visit the city.
Earlier this month, the mayor appointed Dare to help rebrand London’s Docklands area ahead of the Games.
In January, M&C Saatchi picked up a brief from VisitBritain to promote upcoming high-profile events in the UK.