Plans for a massive redevelopment of the Skipton House site at Elephant & Castle will be unveiled next week.
The existing Skipton House dates from the early 1990s and is occupied by the Department for Health. The Government's lease on the building expires next year.
Next week owners London & Regional will hold a three-day public exhibition of their plans to redevelop the site with twice the current volume of office space as well as around 450 homes.
The new development, designed by Skidmore, Owings and Merrill, will include publicly accessible gardens on the roof and the reinstatement of Skipton Street which formerly ran through the site.
"London & Regional Properties are proposing a significant investment in the regeneration of Elephant & Castle, which will celebrate the area's cultural heritage," said Geoffrey Springer, head of development at London & Regional.
"This will be an iconic development, providing new cultural and community space and importantly new jobs and homes. The development will also deliver new open space and a vastly improved public realm, strengthening the ongoing regeneration of Elephant & Castle.
"We look forward to meeting with local residents, community groups and businesses at the public exhibition, to further explain our proposals and listen to what local people have to say."
Cllr Mark Williams, Southwark's cabinet member for regeneration and new homes, said: "This is an exciting new project that will complement and enhance our own vision for the new Elephant & Castle town centre and bring another world class development to the heart of Southwark, creating a wide range of benefits for our community.
"The proposals for Skipton House will transform the gateway into the London South Bank University, create new offices for local businesses, improve open and green spaces around the site and provide even more cultural amenities to the area to put Elephant & Castle firmly on the map."