NHS foundation trusts have been warned that they cannot depend on political pledges to maintain spending as the financial crisis worsens, and must plan accordingly.

Foundation trust regulator Monitor said financial assumptions contained in a review of the three year plans submitted by the 115 NHS foundation trusts were likely to prove “over-optimistic”.

It said: “Planned growth in income is a continuation of historical trends, but may not adequately reflect the potential for lower future NHS funding in the later years of their plans.”

Monitor has ordered FTs to base their assumptions on more “pessimistic” outcomes by preparing “downside” forecasts for the financial year 2011-12.

This follows reports prepared by the trusts based on continued revenue growth after 2009-10 - up 2.1 per cent in 2010-11 and 1.6 per cent in 2011-12 - with costs rising by 1.6 per cent and 1.1 per cent respectively.

Monitor spokesman Stephen Hay said: “Although we have found that NHS foundation trusts are consistently improving the quality and robustness of their financial planning, we are concerned that the plans prepared earlier this year may now prove over-optimistic.”