The AAR is drawing up a shortlist of agencies to pitch for the business.
Adam & Eve previously handled the account, after securing the launch campaign for Westfield London in March 2008.
The agency was forced to resign the business in April last year after it picked up the £20m John Lewis account.
The successful shop will be briefed to build the profile of both projects through TV, press and outdoor activity.
One of its first tasks will be to devise a campaign that will position the Stratford City development as an "industry showcase" ahead of its launch next year. The £1.45bn development will act as a retail gateway to the Olympic Park.
Bill Giouroukos, the director of operations at Westfield, said: "This is an exciting opportunity for a truly innovative creative agency to work on an integrated advertising campaign for two of our global flagship schemes, which represent the two largest urban shopping centres in Europe."