An architectural competition will be run to find a design for the public space around the new headquarters for the Co-operative Group on Miller Street in Manchester city centre.
The Co-op and Manchester City Council said the contest will cover the public realm across the whole 20-acre site, which will include other uses and occupiers apart from the Co-op when fully built out.
There will be a new square in front of the Co-op's head office and another in the complex of listed buildings between Dantzic Street and Corporation Street.
The winning team will be required to create detailed, costed and deliverable designs for the early phase works and deliver a clear vision and material palette for future phases.
Lynda Shillaw, managing director of The Co-operative Estates, said: "We want the area to enjoy an international reputation for having raised the bar for environmentally sustainable commercial development and this competition offers the winning team a fantastic opportunity to create exceptional public realm.
"The regeneration of the site will begin with a new purpose built head office for the Co-operative Group which will be completed in summer 2012 to highest possible environmental construction standards."
Sir Richard Leese, leader of the council, said: "This important 20-acre site stands at the northern gateway to the city centre and will play a central role in its ongoing regeneration, through the creation of a very high quality new commercial quarter. The Council and the Co-operative Group share a commitment to delivering exemplary standards in both sustainable development and urban design."
Construction of the 325,000 sq ft HQ is due to start this month by BAM.