The MOD's Defence Information Infrastructure (DII) project was "badly planned" and suffered "major delays" as a result, an influential group of MPs said today.
The £7bn IT system was designed to replace hundreds of old IT systems, but the Public Accounts Committee, which oversees government spending, said it was "badly planned in important respects".
Committee chairman Edward Leigh said, "No proper pilot for this highly complex programme was carried out."
"Entirely inadequate research" meant the IT was housed in buildings that were in poor condition, he said.
In addition, the Atlas consortium of suppliers led by EDS - a company, according to Leigh,"whose track record of delivering government IT projects has not been exemplary" - underestimated the complexity of the software it had agreed to create. It took two years to deliver a system that could safely handle secret material.
While there has been recent progress, the PAC said terminals need to be rolled out quicker if the department is to meet its latest deadlines. While 3,400 terminals a month are now being rolled out, this will need to be increased to 4,300 if deadlines are to be met.
Leigh also urged the department to turn down any more claims from Atlas for higher costs, if further software errors occur.
The DII began in 2005 and should be finished by 2015. Its implementation has suffered major delays. While 62,800 terminals should have been installed by July 2007, only 45,600 were in place at the end of September 2008.
The Atlas consortium has also slowed the provision of core software because of its "inability to meet the department's requirements". Word processing, internet access and security to run on the new system should have been available in June 2006, but less than half had been delivered by June 2008.
The problems mean existing computer systems have been used for longer than intended, with increasing risk that one or more will fail. The cost of the project has also increased by £182m.