The firm has left the job months before its 60 week contract to construct and fit-out the complex was due to complete.

ISG started the job, known as Project Fox, last February with a scheduled completion date for April 2013.

Site sources told the Enquirer ISG was suddenly replaced last Friday as the scheme’s project manager Mace took total control of the job.

A site insider said: “Mace marched in last Friday and took control, which was the last we saw of the ISG site team.”

ISG and Santander released a joint statement, which said: “ISG has completed its element of the project and it has now been handed back to Santander for the IT-related installation.”

The data centre project near Leicester is the biggest contract on ISG’s books. It includes construction of two identical buildings, each with a floor area of over 161,000 sq ft.

Each building has two subterranean floors, which will contain the computing equipment with the other levels housing electrical and mechanical infrastructure.

The technically complex fit-out of the buildings includes a highly resilient services installation, enabling full maintenance of the 24/7 operating facility.