A group of MPs says the government is incorrect to keep claiming it is allocating an extra £10bn to the NHS in England over the next five years.
The Health Committee has written to the chancellor to say using the figure gives the “false impression that the NHS is awash with cash”.
The group said the figure was closer to £4.5bn and called for more NHS funding in November’s Autumn Statement.
But the government insisted the £10bn figure was accurate.
The Health Select Committee, chaired by Dr Sarah Wollaston, has been hearing evidence over recent months on the state of NHS finances.
Its letter says what it was told by senior NHS figures “clearly demonstrated the financial pressure facing the NHS”.
But it warned that “the extent of this pressure is not sufficiently recognised” by government.
Ministers regularly state that there will be £10bn extra in funding for the NHS by 2020-21.
The £10bn figure is calculated in real terms once inflation has been taken into account and includes £2bn which was announced in the last Parliament.
The health committee says that while the figure is not incorrect, it is misleading because it can only be reached by adding an extra year to the spending review period, changing the date from which the real terms increased is calculated and disregarding the total health budget.
The committee says a substantial part of the extra funding for the NHS comes from cuts to other areas, such as public health.
Dr Wollaston, Tory MP for Totnes, told BBC Radio Four’s Today programme that the head of the NHS had been “very clear” about what the organisation needed, but the government was not delivering.
The GP said: “We are going to be seeing a far more constrained situation and certainly not what Simon Stevens [head of the NHS]asked for.”
Now she is calling on senior cabinet members to meet with her and “increase the priority” of funding the health service, especially in social care.
“The point is that I think the government needs to actually look at the demand pressures in the NHS and social care, which are very unlike other departments,” added Dr Wollaston.
“We really do need some clarity and, if there isn’t anymore money, then to have an honest discussion about what that means for patient care. I think that is what people would like to see.”
‘Pressure is building’
The committee has called on Chancellor Philip Hammond to “seriously consider” finding more money for the NHS – and social care – in next month’s Autumn Statement.
Labour leader Jeremy Corbyn said he agreed with the MPs’ assessment.
Asked by BBC political editor Laura Kuenssberg how much extra funding he believed the NHS needed, he said he “couldn’t put an absolute figure on it” but added: “I do think it needs far more.”
Mr Corbyn said he would pay for additional funding by reorganising the NHS in England to end its “internal market”, arguing the government was “subsidising many private health companies” and spending money on “internal trade arrangements within the NHS”.
Richard Murray, from think tank the King’s Fund, said: “The most urgent priority for the Autumn Statement is to increase funding for social care.
“Years of budget cuts have had a significant impact on older people, their families and carers and are exacerbating pressures on the NHS, with record numbers of patients who are fit to be discharged but delayed in hospital.”
Anita Charlesworth, director of research and economics at the Health Foundation, said: “The Autumn Statement is an opportunity for the government to take immediate action to support social care.
“But for the health service pressure is building, and building fast.
“With funding growth set to slow sharply from 2018, it’s hard to see how the range and quality of services for patients will be sustained.”
The British Medical Association said: “The NHS is already the most efficient health care system in the world. The notion that the funding crisis can be solved with further efficiency savings is a myth, and these are not savings, they are year-on-year cuts that have driven almost every acute trust in England into deficit, led to a crisis in general practice and a community and social care system on the brink of collapse.”
A government spokesman said there would be a “£10bn real-terms increase in its annual funding by 2020-21, for hospitals, GPs, and mental health services.
He said: “It is wrong to suggest otherwise.
“We have also allowed local government to increase social care spending in the years to 2020, with access to up to £3.5bn of new support by then.”
Other parts of the UK have recently reported health funding pressures. Audit Scotland says some Scottish NHS boards may not be able to balance their books this year.