The incumbent on the account, Dye Holloway Murray, did not re-pitch. The review was handled by the AAR.
GMG Radio spent £2.2m in the 12 months to the end of December 2009, according to The Nielsen Company, and Smooth Radio accounts for around half of GMG Radio's overall spend.
KLP will handle above-the-line creative work for the Smooth Radio brand as well as below-the-line and digital, for an initial contract period of two years. The agency will be charged with growing the Smooth Radio listener base across the brand.
Stuart Taylor, the chief executive of GMG Radio said: "KLP showed an understanding of the target audience and clearly have an affinity with the task in hand. They presented us with a series of engaging solutions demonstrated expertise in all areas of communication."
According to the most recent Rajar results, for October to December 2009, the six-station Smooth network had an average weekly reach of 2.69 million listeners, down 6.6% year on year and 3.9% quarter on quarter.
The brand's most recent advertising campaign featured album covers photographed against incongruous background scenes, in a bid to show the range of music aired on the stations.