The Liberal Democrats have put pressure on the government after it was claimed it had gone back on a promise to spend a predicted £1.8bn NHS surplus on patient care.
The move comes after the new NHS operating framework revealed trusts should have a surplus next year at least equivalent to the £1.8bn achieved this year.
Liberal Democrat health spokesman, Norman Lamb, said: "This is yet more evidence that the much trumpeted surplus is being used to save the government's political skin, at the expense of patient care.
"We desperately need to have some honesty from ministers about the NHS finances.
"How much does the health service actually have for treating patients and staff and how much is being held back to provide cover for more ministerial mishaps?"
However, the Department of Health (DH) insisted it was not being prescriptive about what trusts spent the money on, but that it was sensible to have a surplus.
A DH spokeswoman said the surplus – around 2% of the total NHS budget – represented "good financial planning".
"Having delivered this it is prudent to keep it at around this level next year to allow us to respond to in-year pressures whilst being able to commit all the growth money we have received in the comprehensive spending review on new things as opposed to clearing debts," she added.