Some parts of England will not benefit from a modern Fire Brigade communications network in time for the 2012 Olympics.
The news follows further delays in the FireControl project .
The project, which will replace 46 fire control rooms across England with a new network of nine, was originally to be completed in 2009, until the first round of delays moved the date back to summer 2010.
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The project may not be fully implemented until 2012 or 2013, meaning some of the control rooms won't be fully transferred to the new system in time for the Olympics.
The Fire Brigades Union (FBU) said some control rooms that have not fully migrated will be using a "mish-mash" of systems.
Adrian Clarke, regional secretary at the FBU for East Anglia, said, "You would expect an influx of people in the country when you are holding the Olympics. The event could be a target for terrorism and it's absolute nonsense that we will be working with a mish-mash of systems."
The FBU said it has concerns over the IT systems because it will be the first time a 999 system will have a call stacking system. "We believe that this system will not be as effective as they say it will be," said Clarke. "The goalposts were shifted to fit what could be delivered."
The aim of the £1bn project is to improve resilience by introducing the ability to transfer calls to different sites at busy times.
A spokesperson for the Department of Communities and Local Government said, "Schedules for projects of this kind are kept under constant review. The department's focus is making sure the benefits of this project are delivered to the fire and rescue service and the public."