Development group Kier Property has bought the rights to build the remaining phases of the Arena Central project in Birmingham city centre.
The company will also assume responsibility for completion of 3 Arena Central, the new West Midlands hub for HM Revenue & Customs and the Department for Work and Pensions which is due to house 3,600 staff from 2020.
Arena Central is a joint venture project led by Edinburgh-based Miller Developments which has sold its interest to Kier Property for a reported £30 million.
The remaining three plots will comprise office buildings totalling 526,009 sq ft - known as 5 Centenary Square, 4 Arena Central and 5 Arena Central.
The are due to be built in a phased basis over the next seven years but at present no occupier has been been announced for these buildings.
The first building, 1 Centenary Square, was completed last year and is now owned by HSBC UK where it houses the head office of its newly separated retail and business banking arm.
A Holiday Inn Express also opened at Arena Central in 2017 but neither of these are included in the deal.
Tom Gilman, managing director for Kier Property North, said: "We are delighted to announce the purchase of this significant development opportunity.
"This acquisition will substantially increase our activities in the West Midlands and will enable Kier to continue the development of the area as a place where people will want to work, shop and socialise in Birmingham."
Andrew Sutherland, joint managing director at Miller Developments, added: "Having been involved in the project for a number of years, Arena Central is now firmly established as one of Birmingham's prime office locations and we're delighted to hand the baton to an organisation of Kier Property's calibre for delivery of the remaining phases."
Pinsent Masons, CBRE, HFF, Eversheds and JLL acted on the deal.