The move comes exactly a year after RBS appointed Wieden & Kennedy London, following a four-way pitch that featured CHI, as well as St Luke's and Partners BDDH.
CHI did not have to repitch to secure the account. The first fruit of this appointment will break in the second quarter of next year. While no decision has been taken regarding the specific media the company will use, it is likely to encompass TV, print and press.
Tim Lewis, the RBS Group credit cards director, said: "The main reason we picked this agency is that it has three very senior directors who are all prepared to work very hands-on with our business. In many other agencies you would not have such seasoned contacts."
The CHI founding partner Johnny Hornby said: "After all the hard work we put in last year, it's brilliant to be given another opportunity. It's great to be on the roster for the biggest bank in Britain."
Since its creation in 1995, RBS Advanta has relied on direct marketing and PR to build its customer base. The appointment of CHI is part of a new strategy to strengthen the brand by using a broader marketing mix.
The move comes as the Royal Bank of Scotland draws closer to deciding the fate of its £10 million main account, currently held by Faulds.