Lanchin, who was previously the Design Council's executive director of marketing, media and partnerships, will take charge of The Marketing Store's intellectual property, research, insight and planning processes unit.
As well as heading up planning and strategy, Lanchin will work with the business development and creative teams to help the agency win new accounts and grow existing ones.
Before the Design Council she spent eight years as director of planning at Publicis and was Channel 4's head of marketing for eight years prior to that, where she oversaw the marketing activity surrounding the launch of 'The Big Breakfast'.
Simon Marshall, The Marketing Store's managing director, said: "Wendy brings an unrivalled range and quality of experience across the retail and service sectors, both agency and client side.
"She will have a crucial role to play in developing our strategic and planning capabilities."
Lanchin said: "I am very excited to be able to help build a new planning-led ethos in the agency and to strengthen an already very successful offer for TMS clients."
The Marketing Store's clients include Shell, Mars and McDonald's and Vodafone.