Ministers in England have given the wrong impression about how much extra they are spending on health, MPs say.
The government made big play of the extra £8.4bn on top of inflation it was giving the NHS this parliament when it unveiled its spending plans last year.
But the Health Select Committee said the true figure was about £4.5bn.
The MPs said a different definition of spending was used to give the idea of more funding. Ministers have rejected the accusation.
The cross-party group of MPs said instead of focusing on the whole health budget ministers highlighted the amount going to the frontline via NHS England.
In 2015-16 that was about £101bn, but that ignored £15bn of money set aside for other aspects such as training and public health.
This is being cut once inflation is taken into account and means the total health budget rises from £116bn in 2015-16 to just over £120bn by the end of the parliament.
MPs said this was important because the cuts to other areas of spending would have an impact on everything from staffing to health promotion schemes, such as obesity programmes, which have a direct impact on the frontline of the NHS.
The committee also said the scale of overspending last year - NHS trusts finished 2015-16 £2.45bn in the red - would mean large chunks of the extra money being used to cover deficits.
Committee chair Dr Sara Wollaston added: "Whilst the NHS has been treated favourably compared to many other departments, the increase in health funding is less than was promised if assessed by usual definitions."
But a Department of Health spokesman said ministers stood by their figures, saying despite public finances being tight the government had found the money needed.
"We reject these conclusions," he said.
Meanwhile, leading researchers have questioned the government's policy of creating a seven-day NHS at a time when money is so tight.
Rachel Meacock, from the University of Manchester, called for a pause in the policy, saying the arguments made by the government that increasing staffing at weekends would cut death rates were "flawed".
She said pushing ahead with the policy could end up making care during the week worse because services would be stretched.
Prof Julian Bion, who leads an official research programme into NHS care at weekends, said the plans would be "unachievable" with the current level of funding.
He predicted it could even be a "good 20 years" before the policy was fully realised across both emergency and non-emergency care.