He said: "We are still committed to the Anstey development but at present are reviewing all aspects of our operations." The spokesperson said it was unclear how long Marconi's review would take before a final decision was made.
It is understood that the project team, which includes contractor Bovis Lend Lease, cost consultant Turner & Townsend and architect Temple Cox Nicholls, is still working on the scheme.
One insider said: "We are still working on the project but this scheme is under constant review. Marconi is looking at all its sites worldwide."
Work was due to start on site on the project, based on a concept design by US practice Studio Architecture, at the start of the year. Bovis Lend Lease had beaten off bids from Sir Robert McAlpine and Interserve to secure the job.
We are still committed to the Anstey development but at present are reviewing all aspects of our operations
Marconi planned to accommodate more than 5000 staff at the headquarters, which is on the site of a disused airfield.
The telecoms equipment manufacturer suspended its shares at 245p ahead of a profit warning and the announcement of 4000 possible job cuts. This caused the company's market value to plummet £3.6bn in one day. The shares had previously reached a high of £12.50 last September.
The question mark over the Marconi project is not an isolated symptom of the problems in the high-tech sector.