Downing Street "leant on" the chief executive of the NHS to reduce the amount of money he said was needed to fund the health service, a former Liberal Democrat cabinet minister has claimed.
David Laws told the BBC's Andrew Marr Show that Simon Stevens had said to Downing Street that the NHS needed to find £30 billion and that £15 billion could be found through efficiency savings.
But Mr Stevens was then told there was "no way" David Cameron and George Osborne would sign up to providing the other £15 billion and that he should cut that figure down, according to Mr Laws.
The Liberal Democrat told the Marr programme: "At the end of 2014 it was clear that there were huge pressures on the NHS budget. In government our major focus was on getting more money for the NHS in the last year of the coalition in 2015.
"Simon Stevens, the chief executive of the NHS, then decided to go off and do his own piece of work looking at how much the NHS needed over the next five years - in this parliament basically.
"He came up with a figure of about £30 billion that I think was about right and he reckoned that half of that could be made in efficiency savings and that he needed the other £15 billion from the Treasury.
"The problem seems to be that when he then took that figure to the Conservatives in Number 10, they said 'you must be kidding, there is no way the Chancellor and the Prime Minister will sign up to that figure, you better get that figure down if you want it to be taken seriously, you better increase the efficiency savings'.
"He did that, reduced therefore the demand to £8 billion.
"We now therefore as a consequence have the NHS needing to make in this parliament three times the rate of efficiency savings that it has made over the last 20, 30 years.
"I think that's undeliverable and I think those assumptions need to urgently be reviewed otherwise we are going to see the NHS gradually decline in terms of its standards over the parliament."
Mr Laws was then asked if Mr Stevens had been "strong armed" by the Government into pursuing the "fantasy figure" of £8 billion which was widely touted by the Conservatives ahead of the 2015 general election.
Mr Laws said: "I am saying that and frankly Simon did not a bad job for the NHS by changing the terms of the debate in late 2014 by getting eventually all of the political parties to commit to this extra £8 billion.
"But I think he had to make compromises and as a consequence it put into the public domain the sense that £8 billion is what the NHS needs.
"Actually it needs more than that if service standards are to be maintained."
Mr Laws stressed the need for an independent review of NHS funding as he said he was not criticising Mr Stevens.
"He put on the agenda the need to increase the NHS budget at a time when all of the political parties were only signed up to real protection of the budget," he said.
"I think sometimes when you're in the political space people end up making compromises in order to move things on.
"I'm not criticising Simon. I think he was leant on."
The revelations are laid out in full in Mr Laws's memoirs, Coalition: The Inside Story Of The Conservative-Liberal Democrat Coalition Government.