The agencies, which secured their positions on the roster following a six-way pitch, will now take on the charity's creative advertising account until 2011.
In the past, the charity had also worked with Wunderman, which did not take part in the review.
The appointment of a new creative roster marks the beginning of a three-year plan by the Wigan-based charity to up the ante in the war against litter.
In March, Keep Britain Tidy also appointed a digital roster, selecting Rippleffect, Reading Room and Affinity New Media to handle its online marketing.
Those agencies will work range of digital requirements including website design and viral and e-mail marketing.
LONDON - Keep Britain Tidy, the part-government-funded environmental charity, has appointed Inferno to its creative agency roster as well as reappointing its incumbent agencies Dig for Fire and Lake Design.