Central government departments spent more than £500 million on consultants and short-term staff last year to help put flailing large projects, such as Universal Credit, back on track.
An investigation carried out by The Times found that when 'off payroll' staff were included, the figure was likely to be nearer £800 million.
Whitehall has also spent £287 million on staff redundancies during the same period and Cabinet Office Minister Francis Maude had previously put a ban on the use of consultants, unless he gave his express approval.
Despite this, Whitehall has continued to use the likes of KPMG, PWC, Deloitte and Ernst & Young on big IT and transport projects that the government hopes to finish before the next general election in 2015.
A Cabinet Office spokesperson said: "Cabinet Office delivers projects across a wide range of high-profile policy areas. It is sometimes necessary to recruit for specialist business-critical roles.
"Such roles are only authorised where the skills are not readily available within civil service where using temporary labour is better value for taxpayers' money than hiring full-time staff."
The Department for Work and Pensions recently admitted that although its current IT solution for the flagship Universal Credit progamme is viable, it is not up to scratch and is calling in the Government Digital Service for help.
It claims that any 'enhanced IT solution' that is built by GDS to complement the current system, which has been developed with the help of suppliers such as Accenture, HP and IBM, will have to be delivered on time and on budget.