Surname & Surname, which is a play on the tendency for PR shops to be named after their founders, launches after winning its first client, sofa retailer DFS.
The agency starts with six full-time employees and is being led by Lotte Jones and Kev O'Sullivan, who moved from their roles as associate directors at Blue Rubicon. More staff are being recruited.
Jones said: 'We noticed that clients are tired of the ferocious creative agencies that come up with amazing stunts but don't deliver on the day-to-day, and are frustrated with the safe-pair-of-hands agencies that lack creative edge and energy.
'We want to sit in the middle and combine our creativity with our strategic thinking.'
The launch comes weeks after Blue Rubicon opened consultancy arm Thirty Six Strategy, which aims to apply political campaigning to consumer brands.
Blue Rubicon CEO Gordon Tempest-Hay said there was 'more to come', with further launches planned this year.
O'Sullivan said: 'Although we will rest on Blue Rubicon's heritage, we will appeal to different clients and talent in the industry. We're about big global brands and understanding their audiences.
'Both agencies have been created to serve a need that we've heard the industry is crying out for. They will offer new services and thinking. It is not simply a move to pull clients over to different set-ups.'
Surname & Surname won the DFS account after a competitive pitch. The agency will help the retailer connect with upper-middle-class shoppers by promoting its British heritage, as the firm seeks to move away from promotions solely focused on sales and interest-free credit.
Although Surname & Surname will initially be based in Blue Rubicon's offices in London Bridge and will draw on the agency's account experience, it has a separate branding and website.