The NHS will pay private companies £53bn for private finance initiative hospitals worth only £8bn, the Conservatives have revealed.
About 60 PFI hospitals have been built so far
The figures emerged in a response to a Parliamentary Question tabled by Shadow Health Secretary Andrew Lansley.
Under PFI, a private company builds a hospital and then collects "rent" from the NHS for around 30 years.
The government said the comparison was misleading, as the total cost includes cleaning and buildings maintenance.
It says the flagship PFI policy means the private sector bears the risk and cost of building new hospitals.
But unions said PFI schemes were "expensive, inflexible and adding to financial burdens".
There are 58 NHS PFI schemes already open with another 30 under construction.
Shadow health secretary Andrew Lansley said: "Six years ago, Labour promised the biggest ever hospital building programme in the history of the NHS.
"Now, they say they do not want care to be provided in hospitals after all.
"It is perverse that, with hospitals around the country now suffering cutbacks and closures, over 80 NHS organisations are locked into long-term contracts for the building of large hospitals that we have no idea whether the NHS will actually need."
He added: "While there is a key need for private sector investment in the NHS, Gordon Brown has failed to recognise that 30-year-long PFI contracts are often at odds with the Government's concept of competition between hospitals.
"The extra costs of £45bn are completely unjustifiable in the context of an NHS under intolerable financial pressure."
He added: "Every hospital I talk to wants the freedom to structure its borrowing projects as they wish. For all too many, PFI has turned into a straitjacket."
A Department of Health spokesman said comparing PFI capital construction value and full-life costs was like comparing "chalk and cheese".