Carat is one of the incumbent agencies and has held the account since 2002.
Publicis Groupe’s Starcom MediaVest was also appointed last year to handle media planning and buying for British Gas’s Business Services division. It also handled the media planning for the launch of British Gas360 scheme to help businesses reduce their energy use.
British Gas’s media accounts are estimated to be worth around £50m.
A spokesperson for the company says it is “looking at options to consolidate” its accounts as it currently uses different media agencies in different parts of the business.
British Gas was the first of the major energy suppliers to cut its prices earlier this year and has been embroiled in a price war with competitors Eon, Npower and Scottish & Southern.
In February, British Gas reported a 58% rise in profits to £595m for its residential business.