The government has wasted at least half a billion pounds on overrun IT projects, according to figures collected by Liberal Democrat shadow chancellor Vince Cable.
The Twickenham MP described the overruns as the "biggest waste of money in government", and warned that the total losses may be much higher.
Cable has collected the figures by asking each department annually for five years how much each of their IT projects has overrun since it began.
IT projects at the Department for Work and Pensions are running a total of 21 years late and are £315m overbudget. One project the Pensions Transformation Project, aims to improve customer service and efficiency. It is running £169m overbudget.
The Department for Transport's shared services programme will cost £92m - triple the £31m originally planned.
The telecommunications network at the Foreign and Commonwealth Office will cost £240m, compared with an original estimate of £180m.
The total figure does not include any information from two of the biggest departments, the Home Office and the Department of Health. The NHS Programme for IT is now costing tax payers £12.4bn. Cable said the departments had either not answered at all, or had called the information requested "commercially sensitive".
Cable is working on this year's total figure for government IT overspend. He has been prevented from finding out the true scale of the losses because of departments' refusal to answer all his questions.
"It is fundamentally undemocratic, and very unsatisfactory. We suspect that the worst is being hidden to protect the government from embarrassment," he said.