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 said in July that it calculated the true figure to be about £4.5bn.
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. In 2018/19, we will be seeing a per capita fall in funding for the NHS at a time when our demographics [are showing]an increase in our older people.
“The shift from other departments, for example public health, education and training, all the measures we want to put in place to make the NHS sustainable in the long term, are coming under enormous pressure.”
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.”