 Pollock and Hellowell also say that, although the UK government's support for PFI is based on its supposed ability to deliver good value for money, the mechanisms for testing this are skewed.While developing PFI proposals, contracting authorities such as NHS trusts are required to construct a theoretical alternative to the use of PFI, which compares the value for money offered by a public versus a private finance scheme.The publicly funded alternative is called a 'public sector comparator'.