DLKW, which also handles the £4 million Capital FM brand, has not been invited to repitch for the account, which is for above- and below-the-line creative work.
Capital Gold, which runs a network of six radio stations across the UK, is looking to increase dramatically its advertising and marketing spend. The station is also considering development of its first TV work for the brand.
It will shortlist two agencies and intends to make a final decision next week.
"We are seeking an agency to work on the entire Capital Gold brand," Jo Williams, the network marketing manager for Capital Gold, said. "We felt that the Capital FM brand is such a big job in its own right that DLKW should be left to run just that. Capital Gold has a very different music and audience profile."
She added that it was as yet "undecided" if a media planning and buying review would be undertaken.
The decision reflects Capital Radio's move to restructure its operation into two business units - Capital FM and Capital Gold - to build the Gold business into a brand in its own right.
Williams said that the first work would be for the launch of Capital Gold's most recent acquisition, that of Big AM in Manchester.