Over 30,000 young people are on waiting lists to join the Scouts. The movement says it needs at least 7,500 extra adult volunteers to counter the shortfall.
As well as promoting volunteering as a fun and CV-enhancing activity, Luther will target potential Scout leaders by challenging misconceptions, such as associations with child abuse. The agency will also aim to dispel worries that leaders could be sued after an accident. It will stress that the organisation offers helpers full training and insurance.
Another element to the campaign will be to highlight Scouting's relevance to modern society, including the fact that IT and PR are among its most popular badges.
As well as targeting national and regional press, Luther will encourage businesses to make it easier for staff to volunteer.
The campaign will be timed around next July's World Scout Jambouree, the pinnacle of the group's centenary celebrations. The event will include high-profile scouting activities and expeditions - such as a Mount Everest climb - giving Luther plenty of potential news hooks.
Other initiatives, such as a TV documentary and a commemorative coin, are under discussion.
Six agencies pitched for the two-year account, which was put up for tender in May (PRWeek, 26 May).