Contract value for the five-storey Northumberland County Council Civic Building and associated infrastructure works is put at between £35m and £80m in the contract notice.
The 12,815 m2 office development comprises basement, ground and four upper storeys, with a concrete superstructure and brick and stone façade.
Arch Development Projects is taking the project forward in partnership with the county council.
The council describes its new headquarters as an ‘invest to save’ capital scheme which will save £630,000 a year compared to staying at its current site.
The new building will form part of the wider Portland Park development in the town and construction could start by October 2016, with staff moving in by end of 2018.