As a result of her promotion, TBWA is looking for a new UK managing director for Stream. Summerhayes will initially divide her time between Stream's London and Asia-Pacific offices.
Summerhayes said: "The launch of Stream\Asia-Pacific is testament to how brands are now responding to the changes in the media and technology landscape, by adopting brand entertainment as a serious part of their communications mix on a global scale."
The opening of the Asia-Pacific office follows Stream's expansion across mainland Europe last year. The network now has offices in countries including France, Germany and Finland.