£5.7m Church Square House Office development for 2018.
Work started on site at the start of 2018, for the £5.7 million Church Square House extension in Scunthorpe.
The work comes as part of the council's £60 million investment into the Church Square area
A ceremony was held in January to break the ground at the site ahead of work beginning on constructing the extension to the North Lincolnshire Council building, where 600 of the authority's staff will be based.
Staff will also be moved from the Civic Centre to the extended Church Square House.
The plans come as part of the £60 million investment into the town centre announced by the council in July last year. Simon Green, executive director of commercial at the authority, said the project forms part of the council's plans to make work more flexible.
Councillor Rob Waltham leader of North Lincolnshire "The moving of staff into Church Square will allow them to be more flexible and more productive," he said.
"The clustering of services will allow for more public and private investment in the area as it becomes a place of work for people."
The investment into the Church Square area includes a new office for social landlord Ongo Homes, accommodation for the health authority, investment in Scunthorpe Library and the University Technical College.
As part of the extension, Britcon will be constructing the new offices.
Mr Green added that further developments are expected on the Church Square area.
"The offices will cater for 250 Ongo staff," he said.