LONDON--Ketchum London CEO Avril Lee is stepping down from her role after a decade with the Omnicom Group agency.

Lee's decision will see her remain at the firm until April. Ketchum Europe CEO David Gallagher has taken over as interim CEO of the London office until the search for Lee's successor is completed.

Lee said that she was "proud" of the double-digit growth the agency has experienced under her leadership, despite difficult economic conditions. Ketchum London is now the largest office in the global Ketchum network.

"After many successful years leading the company now is the right time to leave," she added. "I’m looking forward to taking on a new and exciting challenge and know that I leave Ketchum London in great shape."

Lee was promoted to the CEO role in 2011, after three years as deputy CEO. Prior to that, she spent four years heading Ketchum's healthcare practice, following her arrival from Chandler Chicco in 2003.

“We are grateful for Avril’s achievements during her time at Ketchum," said Gallagher. "We thank Avril for her many years of service and wish her all the best.”